Around here a finished horse that can do all of those things might go for as little as $7500 and that's if he is past his prime...BUT
If I had $4000 and wanted a hunter/jumper, I'd start shopping for a nice 6-7 yr old TB or TB cross that had a good start on her/him and start doing some training myself. As long as the horse had a good foundation to build on (and didn't have any physical issues) why couldn't you just keep training with your trainer and use the novice level shows as your training grounds?
I think that would be a very respectable place to start with $4000! Plus, your investment might double or more over time if you continue to work with experienced folks that are as successful as your trainer. Pretty soon you'd have people asking to buy your horse out from under you.
Meanwhile, you can always ride others' horses and compete with them on higher levels....but there is something really special about bringing a horse up the levels by yourself!
Anyway, that's just what I think - horse shopping is a blast - you are going to have so much fun!