Comparing that model and price to other Glock 22s on gunbroker it sounds like a fair price, especially with the additional magazines. A cursory look on the site reveals three Glock 22s, two at $449 and one at $440 and none offered as many magazines as the one you mentioned.
I'm a bit late on this, it was my duty gun too & I like them. They are very accurate,reliable,& easy to shoot. I like the way they sit low in your hand recoiling straight back. Recovery time is really fast. With the issue Rem 180gr jhp I got just under 1000fps. As a defence gun I feel there are very few better, & with the extra mags going with the deal I'd say it's a good buy. Frank