I'm surprised that the reconditioned G17 costs more than the new one. Maybe it's just my dealer, but the factory reconditioned G17s I've seen, even with hi-caps, cost less than a new G17. I guess my dealer figures that the main item being sold is the gun, not the magazines. The hi-caps that come with reconditioned Glocks are used, not new, and he sees them primarily as a sweetener. It's getting harder and more expensive to find factory hi-caps, but they're still out there.
That said, the best magazines for a Glock are made by Glock. Some aftermarket mags are probably okay. But I personally believe that the odds are against your finding a truly reliable aftermarket Glock mag. Also, some aftermarket mags are made of steel and will damage the plastic mag catch of the Glock pistol.
Anyway, I've purchased several factory reconditioned Glocks (G17, G19, and G22) and have found them all to be functionally excellent. In fact, I'd assume that all reconditioned Glocks are functionally about the same. OTOH, the cosmetics of reconditioned Glocks vary from chewed up to perfect. If I were going to pay $529 for a reconditioned pistol (and, to me, this price really does seem high), I'd want to make sure that it's as good as new or nearly so in every respect, cosmetically as well as functionally.
JMHO.