Lance, you are not charging enough for these modifications. That being said, you are still obligated to finish all of these nice peoples' saxophones in a timely fashion. There are millions of excuses to be invented. That being said I feel excuses are nothing but complete bull-****.
Finish the saxophones at the agreed-upon amount, return them to their rightful owners, and immediately increase your prices on all your products/services. You obviously need to. These are intense mods you are doing. People charge $1500 for an overhaul these days.
Do yourself a huge favor and tell the truth to these folks & send pictures of their instruments in their current state to them. Your reputation is on the line here, I think. I know you are far beyond capable.