I agree 5k for an older trail horse is a lot. Even for a packer. I'm on the cheaper side so I'd say about 2k-2.5k. With this economy you can get a decent jumper jumping about 3' for 2-3k.
Also any signs of arthritis in this horse yet? Does she have good teeth, any health problems?
Edit: Sorry iridehorses
. Didn't see your post till after.