I done see any fluid loss at the caliper. What your describing sounds more like master cylinder failure.
Edit: just read the rest of the thread. Tough break. Odd to see that many parts "fail" at once if everything else was working normally.
By my count master cylinder is a $200 part and 2.5 hours labor at $65-100/hr. I'd charge 2 quarts of brake fluid to get everything bled thru well at $15/qt. Call it $480. $900 is high unless they're also charging diagnostic time at 4+ hrs.... Way high on time.
If caliper is bad, that's roughly a $70 part, plus $30 hose. Call it a half hour labor. That's $150
Have you seen your brake pads? If it needs pads, call that $100 in pads, but if you still have pad left then those can wait. If your braking was smooth before, I'd also wait on the rotors. Replace the one that's gouged if you're concerned about it. $85/rotor.
These are rough estimates, but they should be pretty close. The totals I figured at $100/hr - varies depending on shop and region, but you've got a rough time estimate so you can figure if you know what they charge/hr.