For just R&R gaskets and studs/labor, that's about right. To 007's point though there's a lot more that goes into doing the job correctly that that price point isn't gonna cover.
Machining the heads/replacing them if they're cracked (one of the more critical points IMO) usually brings the price up to around 5k when you're having a shop do it. Then having all the "while you're in there" repairs/replacements/updates and such usually tacks on to the job.
Ask the shop what's actually done with that $3500, and what their warranty policy after the work is done.