I was gifted a 20year old Specialized (with 105) last year. I put 500 miles on it before I started getting trouble. Overall it is in good condition frame, BB, seat, wheels are good (aged but solid). However the cassette, chain, and front chainrings are worn (likely original). LBS said it could be $500 for this and new derailleurs (front and back). Closest comparable new I'm seeing locally is $1300 or more. Am I looking at a money suck and should I cut my losses now?

Yes it does need the work, the chain is flying off the dears and forcing me on the shoulder for every mile or so, this no longer an enjoyable ride. Still waiting on a written estimate.

Curious what you would do?