A dilemma indeed!
Are you a prolific quilter? Have you used one before?
What you need to figure out is how many quilts you're actually going to quilt on it before it/you expire. Try and work out how many you do a year - say 10 - times the number of years you think you'll be able to quilt - say 20. That means you will quilt 200 on it. Divide the cost by this $15,000 by 200, means that each quilt will cost you only $75.
However you will need to factor in maintenance, repairs, running costs etc. and consider the amount of room it will take up.
I'm lucky to be able to hire the Gammill at my LQS for my bigger quilts - the rest I do on my DSM.
Good luck!