If you make your own you can expect to pay about $30-$40 to make a whole
slew of them. (I got 11 hoops out of my first batch – keeping in mind I
made several for small children.) Cost varies depending on the size and
PSI of the tubing you choose and whether or not you need to purchase a
PVC pipe cutter.
Hoops need to hit you when stood up somewhere between your belly button and your nipple line. Smaller than that (like almost all store bought ones) and they are nearly impossible for an adult to use. Homemade hoops are heavier too – which makes them easier to keep up.
The link above is what I used when I made mine. Other than the decorative tape (which wore off over time) they have held up perfectly.