This is going to go on all three SW RPG forums, so sorry if you have to read this more than once.
In game the major bad guy (Lets call him Captin Jacka$$ for now) has been planting tracking devices on the PC's ship and we have always found them.
So what if the PC's commission a new ship that all in all looks like and act like the bada$$ ship from the Mass Effect games? would be nice to see a ship builders guide like was done for the Babylon 5 RPG.
Commissioning a new ship design is going to cost a ton of creds. They need to pay for material, labor, design fees, testing of the design to make sure it is space worthy, and dry dock time at the very least it will also likely take 6 months or so at a minimum to design and test and then another 6 months or so to build.
The reduction of consumer price with "stock" vehicles is to to mass production.
Also, if you have a unique ship, then there is really no need to track you as the ship arriving would set off warnings.
Eh, doable. Some crazy shipbuilding guide would be nice, but it's hardly required. Mostly you can just take what you want and find something comparable, though with a little work you can certainly figure out how to custom stat things out.
So... something like the Normandy?
You want to go with the SR-1, SR-2, or something a little more suited for an RPG party that doesn't require a huge crew?
The SR-2 as she is sweet as.
Rules wise, I'd say copy the stat line from the CR90 Corvette, in that they approximately fill the same roles. If you want the stealth effects, copy the TIE Phantom special rules in Stay On Target.
Plot wise, what you're describing isn't exactly technology that is readily available in the universe, so you'll have to:
They want to commission the design and construction of an entirely new model of starship with the size and feature set of the Normandy SR-2?
I hope your PCs have about 50 MILLION credits lying around. 
They'd also probably have to wait about 10 YEARS for delivery. 
SR-2....
Ok, so lets look at things like the DP-40 Gunship, or Marauder as the base, and work out.
Sil 5
Speed 4 (Fast, can keep up with most fighters)
Handling 0 (again, good for a Sil 5)
Def: 3/2/2/2 (noticeably good shields, important because...)
Armor 4 (light armor to save on mass)
HT 65, ST 35
Hyperdrive:x1/x15
Navcom: yes
Sensors: Long
Crew Complement: 35 (esitmate)
Carried Craft: May carry a total of 6 Sil worth of vehicles, with no single craft exceeding Sil 3 (typically a Shuttle and an armored ground vehicle.. I'll leave the hammerhead/mako argument for your table)
Enc: 180
Passengers: 8, +8 more in cryostasis (Assuming many of the Party NPCs from the game count as passengers and not crew)
Consumables: 6 Months
Cost/Rarity: 6,500,000 Credits/9 ® (using the Baudo as an example of a custom built ship, it's double the average cost of a comparable vessel and Rarity 9, add in the weapons and stealth hardware and you've got your extra cost and the Restricted rating)
Hardpoints:0 (It's a purpose built ship, no room for expansion beyond what your rigger can squeeze in)
Weapons:
Light double Turbolaser foward (Thanix cannons)
Double Proton Toropedo launchers forward (Disruptor Torpedoes)
2 Autoblaster turrets 1 Dorsal, 1 Ventral (Guardian point defense lasers)
Additional Features:
EDI: Counts as socket mounted Astromech, See Stay on Target
Amenities suite, Steath Coating & Baffeled Drives: See Fly Casual
And there ya go... if anything I think the 6.5 million credit cost I give is pretty cheap for a stealth frigate with that kind of capability....
And there ya go... if anything I think the 6.5 million credit cost I give is pretty cheap for a stealth frigate with that kind of capability....
That would be a good retail cost on the consumer model, once the initial design, development, prototype, and approval stages have been completed. Oh, and that would be for the first version, after which you could do the revised version for the SR-2.
Look at the one-off cost of a single Concorde SST aircraft versus the cost of developing the entire Concorde programme.
I'd generally say that weapons and ship development would be beyond the scope of most campaigns and, those that it would not be beyond, would be epic and money would no longer really need to be tracked. It would even be most likely the focus of said campaign.
If I really wanted a party to have a ship like that, I'd be more inclined to:
A: have the party hired to steal the ship from a secret repair facility by their friendly neighborhood Hutt, assuming that they were far enough along XP-wise to handle something like that... Do they keep it, earning the ire of a Hutt cartel? Do they return it, but beg for the chance to use it in the Hutt's name? What about the Corp they stole it from? So many options, so much Obligation... either way, they're on the run in a bad ass ship...
or
B: Re-skin an existing ship. It just looks like that now (although the stat block above is pretty solid).
And there ya go... if anything I think the 6.5 million credit cost I give is pretty cheap for a stealth frigate with that kind of capability....
That would be a good retail cost on the consumer model, once the initial design, development, prototype, and approval stages have been completed. Oh, and that would be for the first version, after which you could do the revised version for the SR-2.
Look at the one-off cost of a single Concorde SST aircraft versus the cost of developing the entire Concorde programme.
Star Wars starcraft costs are really wonky, so nailing down a price is tricky.
My thinking was the Marauder Vette and Correlian Gunship are 3 and 3.2 mil respectively, and are probably in a similar weight class as an SR-2 type craft. The core vessel isn't really that complicated by Star Wars standards, which doesn't help either. The Baudo, a custom built to order craft is roughly double the cost of a comparable mass produced ship, so that was kinda the start of my thinking, then I added the cost of some of the high end attachments (especially the stealth gear) and rounded it up to an even 6.5... Which I concur still seems low offhand.
Comparing tech levels of Mass Effect to Star wars is tricky too. If you think about how some depictions of Star Wars history show hyperspace travel in a nearly literal stone age (some old old republic craft are made of freaking STONE?!?! WTF?) it's really bizarre. So it's a matter of how both settings look at technology. Mass Effect is fairly real world feeling sciency take, or at least does a decent job of pretending to be. Star Wars on the other hand really doesn't care for explaining the ins and outs of how it's tech works, making more just a "Yeah, it just works, and everyone knows it works and how to the level they don't need to explain it to each other, ever."
And real-world costs are also difficult to tally. In the real world a new system has to run through dozens of simulations, developmental, and operational tests before it goes on a real deployable status. How much of all that process can be skipped through the use of extremely fast computers, AIs, and Droids in those respective universes saving how many credits?
The end result is you have to make a call.
I'm with Bishop69 on this one - if my players wanted something like this, I'd run them through a heist/theft adventure to steal a brand new prototype ship from someone else. Who they'd steal it from would be driven by the campaign setting; in an AoR game like ours it would be the imperials, an Edge game might be a Corp or from a Hutt syndicate, etc.
Sure - maybe it's an Imperial prototype stealth corvette... wouldn't the Rebellion love to get their hands on it...? or an anti-pirate corporate gun ship...? wouldn't the Hutt's love to grab it... or maybe... (you see where I'm going here).
The story is the thing... the realities of building the **** thing? no thanks. the 'realities' of bombing around the galaxy, evading whoever and chasing whats-its? hell yes.