We had a Glock20 for sale here $450US was an absolute bargin, took nearly a year to sell.
10mm ammo is expensive, but reloading can bring the cost down substantially.
Not sure how easy 10mm projectiles are to come by, but if you can get CMJ (copper plated) the cost is mice nuts.
Im reloading 9mm with CMJ projectiles from Frontier Bullets (South Africa) for about $6US per 50 rounds (using my own brass, federal primers and ADI powder).
CMJ doesnt handle high velocity but would great practice rounds, load some FMJ or JHP for your defensive rounds and keep a small quantitiy aside.