I'm glad you did pay for any of those models with errors. A few things that might help is to find yourself a reputable model maker and stick to them. Also ask them for referrals. Usually, good model makers know other good model makers too. Always stick to the 3d printing category of this website only. Since you have no interest in gaming models or VFX, there's no sense in looking in the other categories. Also, on this website, the quality models are typically more expensive. You should be able to see a lot of preview renders, wireframes, and perhaps even printed photos of good 3d printable models before you purchase. I wouldn't trust any 3d model that does not provide a lot of information with the product, nor any product that only has one screenshot of the model in the software. There should be, at the very least, multiple views of the model from different angles, including wireframes to show you the shape. The description should include scale as well as provide more information about the quality and the uses of the model.
Good luck.