I built one this year and so far it's working great. I got the motor at walmart on clearance last year. Noticed they are selling the same one this year for ~$35 (motor, electronic unit box). I got a couple of large 55 gal plastic drums cut the end off of one and cut about 1/3 of way down on the other to make a make a cap that slides right over the other one. Welded a quick stand together. Also bought the solar recharging unit and battery from walmart. I have about $75 total in it.
It's working great so far, was out there yesterday and cows had discovered it but deer where I'm at don't mind cows. And since they still have good grass they aren't on it every day. Last year my son shot a deer that was going between stands of woods with the cows camouflaging itself. Wouldn't have believed it if I wasn't standing there watching it. As soon as the deer needed to go a different direction than the cows were heading it bolted into a dead sprint since it was in the open, he had to shoot it on the run before it jumped a fence off our property.