Most of them are real and not expensive. Tengchong is the birthplace of jade processing. Most of the jade purchased in Tengchong is genuine, but a few unscrupulous merchants pass inferior minerals off as jade. Because there are more imported wool locally, the price of jadeite will be relatively cheap.
Your question can't be asked like this. The jadeite sold in Tengchong must be A, B, C or counterfeit, so you should carefully identify it yourself. The price level is relative, and one thing and one price cannot be generalized.
Cheap, poor quality, few fakes. If you want to buy something particularly good, you'd better find something that you can understand. Experts sometimes misjudge some super-A-grade jadeites (non-pure natural A-grade jadeites) with special local materials, and the instrument identification is the most scientific.