How much do you think it would cost for you to make? They probably don’t net $200 once they sell one. Mount, prop , exhaust, and drive, if you subbed it out, would be in the ballpark. Once material, rent, labor cost, electricity, tooling, and time designed. Not many work for less than cost.
Every one of these drive designs bother me not having a strut to support the prop side of the pulleys. And the no TBO; chunk the engine and get another is great as long as they keep making them. Do you need to keep a pair and a spare just in case?