Virginia has this: Automobile Repair Facilities Act

I don't know if the following can be applied to machine shops, but I had to pull this out w/ a body shop a couple of years ago when the final went way over 10% of the original estimate w/o any attempt by them to contact us about the additional work:

"B. Where a written estimate is requested, no repair work on the motor vehicle may be undertaken, other than such diagnostic work as may be necessary for the preparation of an estimate, until the written estimate has been provided the customer and the customer has authorized the work, either in writing or orally, and no charge for repair work in excess of the written estimate by more than 10 percent or, in the case of any motor vehicle which is at least 25 model years old, 20 percent or extension of the time for the work may be made unless the additional work represented by such excess charge or the time extension has been authorized, in writing or orally, by the customer."

Nope, we didn't' pay the upcharge...