I've had one for 2 years that I bought for about $10. It works great.
I also work/workout at a gym that has the one you mentioned. It works great too, but in exactly the same way as my cheapo model.
The cheaper model has two skinny wheels in the middle of the handle which is great because I can take the grips off the handle, spread the wheels and do one-arm wheel stuff.
The more expensive model looks nicer and has the loops for your feet which I've experimented with, but never really found much use for. There are plenty of other exercises that are better for developing Glute/Ham strength than this attachment, IMHO. The movement demonstrated on the website with the feet in the loops and drawing the stomach up in a pike position can be practiced on a hardwood floor in socks. Not worth the extra $$ if you ask me.
Of course you could always get a set of rings for a little more and do all of the exercises from the ab wheel on the rings plus about a thousand more. Rings are also more adjustable to your strength level which is great for learning progressions to really hard stuff, like standing wheel work.
Anyway just my two cents.
For fun when you get your wheel try this:
Have a buddy grab your legs wheelbarrow style and wheel you around as you stay 'tight' and 'hollow'. Going backwards is hard, as is changing direction and turning. Go slow in the beginning. Funfunfun.