As someone who just built a house and had a medicore experience with a contractor who constantly misquoted on materials I can understand frustration at the situation. We had several months elapse between signing the contract and him starting work, but every quote on the build sheet was a mile off. Materials were more labor was more and everytime he called something was gonna cost more. I took the increases as a chance to do more work on the house myself, and cut his people out as much as I could. We sacrificed a lot of things we wanted and a lot of compromises were made to make sure it was as energy efficient as it could be so there werent issues later. Lots of the extras were to meet new town mandates for new energy code but he knew of this when he signed up to build it. If you can build it without a GC I highly suggest doing it. Yeah its a lot more research on your end but you get a chance to vet every sub you hire and make sure you get exactly what will fit your budget. If you can just have it framed and plumbed and wired, you can do the interior work yourself if you are handy, it aint that hard to do. Good luck