If they're making more than $5-10 dollars per book profit, I'd be shocked.
The bigger bulk you print the cheaper it becomes and if printed in say places like china et.. even cheaper. Take the I-phone, it only costs a few dollars to actually make and sells for hundreds of dollars. FF Makes good money of their numerous product lines and they showed that in their one announcement(which I have no clue where the video is. The one from the big convention.)
The bigger bulk you print, the more stock you have to sell. Stock sat in a warehouse costs more money in the long run, and doesn't return the money invested in its publication. Stock sat on a store shelf makes the store less likely to keep ordering (because the stock they've already bought hasn't been sold). Over-printing is detrimental to RPG publishers, because RPG publishers are small companies who live and die on consistent cash-flow.
Board games and miniatures games turn around far bigger numbers than RPGs. RPGs are a cottage industry, where even the biggest name in the industry (D&D) has an in-house team of four people, and 90% of the development work is outsourced to freelancers.
I'll quote some numbers from another industry example I've seen.
Let's take your average 400-page, full-colour hardcover - roughly comparable to the item you linked upthread. Let's further presume that it's a creator-owned IP, produced entirely in-house, so no licensing fees apply, and that it has no photographic interior illustrations, so it can get way with using non-premium ink and paper.
Right off the bat, it's going to cost you about $20 per book to manufacture the thing, once production, freight, warehousing, applicable taxes and other expenses are properly taken into consideration. It could be substantially cheaper if we were talking mass-market distribution, but a typical tabletop RPG (i.e., not one of the Big Three) will be fortunate to move a thousand units in its first year, so the economies of scale are limited.
That's just to produce the physical book, though. What does it cost to get there?
Well, there's writing, for one. For a 400-page manual, you're looking at about 120 000 words. A reasonable rate for this type of writing is $0.7-$0.8 per word, but the pay for RPG writing is notoriously now; let us assume we're paying a mere $0.03 per word. That's $3600 in writing costs.
There's also editing. A decent editor will easily run you $50 per hour. Presuming we're talking about mere copy-editing (i.e., no major structural editing is required), a 400-page RPG manual is about a sixty-hour job. That's $3000 in editing costs.
Let's not forget illustration, either. A book of this nature would be expected to have at least one illustration every 3-5 pages - let's call it an even 100 illustrations. Costs here are highly variable; a full-page, full-colour piece can easily run you $500 or more. Let's generously presume, however, that the average cost per illustration is only $50. That's $5000 in illustration costs.
Then there's the layout to put all this together. Layout for print is a much more complicated proposition than simply whacking everything into a Word document and calling it a day. As with illustration, the costs here are hugely variable depending on your level of ambition, but let's lowball graphic design and layout together at a mere $2000.
There's also a whole bucket of miscellaneous expenses, ranging from commercial font licenses, to ad banners and promotions, to playtester compensation (which typically comes in the form of food and free merchandise rather than cash, but it adds up), and so forth. Let's eyeball this at another $2000.
(Note that I'm valuing my own labour as project manager at essentially zero here. If I also wish to be compensated for the probable 500+ hours I've put into arranging all this, that's another expense - but lest I be accused of padding my own pockets, let's assume that I'm a deranged nerd who's willing to work for free.)
That's $15 600 in expenses, all told. Divide that out over the expected one thousand sales in the first year, and we've got $15.60 per book; on top of the $20.00 in production costs, that's a cool $35.60 per unit.
$35.60 per book. Those books will retail for $60 each, of which the distributor/retailer combo takes 40% (a low estimate here), so $24 of each copy never reaches the publisher. $36 left... so about 0.40c profit per book. $400 over all thousand copies.
And some of those estimates are low-end. Most smaller RPG publishers get by through consolidating jobs together - it's common for editing or layout, plus some of the writing to be done in-house by the guy who runs the company.
FFG makes a few economy of scale savings - they've got in-house staff for things like editing and layout (spread the cost across many projects), in-house project managers can write text as part of their salaried work, they're a noteworthy, successful brand who can more effectively negotiate with distributors, and they make things other than RPGs, so they've got a range of resources that don't fall into the costs of any single project (I imagine things like graphic design assets, fonts, etc for Star Wars are a collective resource for all Star Wars products FFG makes), which saves them money and makes it more profitable overall... but it's not going to make a colossal difference.
RPGs aren't something you do because you want to get rich. Even for the big companies, RPGs make pitiful amounts of money. Wizards of the Coast downscaled the D&D development team to a half-dozen people, and outsources the actual writing to freelancers, because with D&D, the intellectual property (the name "Dungeons & Dragons", the imagery and cultural cache, the movie rights, the novels, the computer games and board games, etc) is worth far more to Hasbro than the RPG itself is - they keep the RPG around because it'd be bad publicity to let the game go out of print when you're trying to make money off the IP.
If artists are underpaid and underappreciated in the RPG industry, it's because everybody is underpaid and underappreciated in the RPG industry... and that doesn't change without the retail price going up, because the margins are already tiny.