If you want new factory-built, you might consider just paying retail price or working with local dealers to get rock-bottom markup. You could save yourself a lot of hassle and the markup isn’t really that much compared to the costs you face anyway. Your market sounds like it could support resale after a dealer’s markup. In the alternative, you’re the dealer. Do you have a dealer’s license? Or are these for rental?
I would “estimate” basic box $34k plus shipping, installation, hookups, skirting, decks & stairs, and perhaps A/C. You can probably go a little up or down from there but you said 3/2. That’s a complete ballpark guess, btw.