So, in SW Magazine recently, what was actually the first piece of the new canon, has Blade Squadron, which is a squad of B-Wings, taking out the Executor during the Battle of Endor.
If a single squad of B-Wings can bring down a behemoth like that.. why can't two Corvette's bring down a Victory-Class?
Hell, an A-Wing brings down a Star Destroyer by crashing into its bridge!
I'm really not sure where the idea is that a well-flown pair of Corvette's shouldn't be a threat. By the looks of it, if the Corvette's stay in the front arc of the VSD, they will get destroyed rather quickly as they'll be taking between 6 or 9 dice to the face vs 2 shields. But if they outmaneuver the VSD? All of a sudden they stand a chance, and since they're more maneuverable, they're potentially able to do that, hence their comparative cost.