I just traded an 06 HPX for a 07 XUV. I received $8189 for my 06. The list on a new 07 HPX is $8495 but mine did have a few options on it. I had the bed lift (which was a $1001 option in 06), bed liner, floor mat, horn, rear hitch (standard on 07) and the deluxe light kit which gives you tail lights, brake lights, turn signals and 4 way flashers. My XUV has those options plus I added a few others. It had 44 hours.
A 07 HPX will list for $8495 but if you were buying it outright the dealer should give you about a 10% discount (there is less of a markup on gators vs compact tractors). That would put a brand new HPX gator at about $7650. I would think you could do a little better than $7500.
The dealer probably has a pretty good amount in the HPX from a XUV trade. If that 06 HPX is stripped down, you can do better. If it has the lift, then that is probably a fair price. The 07 lift was reduced in price to somewhere the $750 range so that would put the list on a new 07 HPX at around $9250 with a discounted price in the neighborhood of $8350.