How much does it cost to deal with they dug and graded and parked right next to my tree during the build, and now it looks bad?

Assessment first, and it is worth paying for. A root-zone evaluation may include exploratory excavation with an air spade to see what was actually cut, priced by area, and that is the honest way to answer 'how bad is it.' Ongoing care is watering, mulch, and compaction relief on a multi-year schedule — recurring but modest. Removal, if it comes, prices high for this symptom specifically: the tree is now surrounded by a finished house, new hardscape, and fresh landscaping, so access is worse and everything gets rigged or craned. If an insurance claim or builder dispute is in play, a tree appraisal is a separate professional service and must be documented before removal, not after.