If your Kay is in good shape (never had the neck broken or the top kicked in, for instance) you didn't pay too much in the sense that you could get your money back out of the bass. This bass was the subject of a recent thread
http://cgi.ebay.com/KAY-VINTAGE-UPRI...QQcmdZViewItem
and it went for a little over $1800 bucks. The bigger question might be whether or not you like the sound of your bass. My understanding is that the Kay likely has a rosewood fingerboard now - the harder ebony board would likely give it more presence and sustain. (Note : I've read here recently that many of our luthier members are out at some show/conference - you might want to wait till they get back on TB and get some good advice

) So, if you like your Kay now you'll probably like it a little better w/a new fingerboard - if you don't really like it now, sell it before you put any money into it and you could probably get back what you paid and put that money toward a different bass. I think if you start to get $2500 bucks and up invested in your Kay, you'll never get that money back out of it. Then again, I have a German carved factory bass where I spent $2k on repairs (involved taking the top off, etc) a couple of years ago. Considering the purchase price of that instrument, I probably couldn't get my money back out of it. But my decision was made because I really liked that bass and we have a long history together. I haven't regretted it.
On the other hand, I think about selling my Kay about every other time I play it - it's set up well and sounds OK, but we don't have that history together and I think about how I could take that money as a down payment on a New Standard or such. So, this is a long and rambling reply that says I'm mostly on board with drurb's reply.