The cost on a power windmill gives about a 50% ROI over the life of the windmill.
Mine would be verticle and home made. And I’m not doing it to save money. I’m doing it to augment night time power at my place here. We get horrendous wind sometimes. Heck, we have a couple of streams on our property. We might even want to throw in a waterwheel or two some day. And with all the wood on the place (32 acres, about 60% wooded) someone suggested steam power for those times when solar and wind don’t cut it. Seems like a lot of work, though.