Please don't spend all that money on something that you will only need for a few days. Cushioning with pillows is enough. Just remember not to sit on a very low chair and to take things slow in the early phase of healing.
I usually recommend that my patients sleep in a recliner after a tummy tuck if they have one. If they do not, I think it is an expensive and unnecessary purchase as you can achieve similar results with a few pillows you already have behind your back and underneath your knees. Good luck.
Following a Full Tummy Tuck, anything that keeps you in the "beach chair" position will work. A recliner, if you have one, works well for this and it is easy to get in and out of. However, a contour body wedge or 2-3 pillows in your bed comes in a close second. Good luck with your surgery!