IF it's the Primestar (Channel Master) 1.2m dish (and it does seem to be that one. They are real rare in my area, I have only ever seen a single one) it's well worth the $100, especially if the non-penetrating mount comes with it. Heck, even if you don't want the mount (at least take the mast post) I would NOT however pay that price for the slightly smaller 1m Primestar dish.
That dish at the 1.2m size is nearly unbeatable (especially) on a polar mount for signal gathering compared to any other dish! You will need a donor polar mount from at least an old 6 foot dish, as the OEM polar mounts for these dishes are extremely rare in the wild, and you will never likely find one.