Any ideas on how much I have to spend in order to get prisms that are good? Any one use the stuff from China and is it any good?
The ones we buy are SECO and are about $125 each. That doesn't include a tribrach though.
We have had problems with them, in the past, breaking from the plastic at the back. It's typically after several years worth of use. If the housing holding the prism was metal, I'm sure we'd still be using that prism. Otherwise, we are satisfied.
I'd try a cheap one from China, if it was really cheap, and the distances checked on my baselines with what my other prisms are. In a perfect world, I'd borrow one that someone already bit off into, but if it's like $25 or something, I'd probably do it anyway.
I have several of the $30 china targets with Seco prisms installed that were in use with Seco tribrach (which appear to be better quality made in China).
I have replaced those with Sokkia and Lietz tribrach (searching and waiting for listings on EBay mostly).
Prisms have to be handled with care because of their plastic case.
They do not take impact very well and once cracked lose their waterproof status and will fog more often.
I did not hesitate to begin with several $90 units that would last long enough to be able to replace them with better quality lifetime equipment.
Seco prisms are pretty good; I wouldn't buy anything less than that. I'm not sure that there expensive ones are any better than their less expensive ones, based on recent experience. I just got one of these today, it's pretty nifty:
https://www.surveying.com/en/mini-prism-mono-pod-kit.html
I use the Leica mini-prisms (GMP101) almost exclusively. I have a couple of Leica full-size (GPR1) prisms that I use rarely when I need to shoot over 1,500 feet or so, and a GRZ4 360?ø that I use even less often because it's so big and heavy. The GMP101 is well made, durable and a pleasure to use. They're well worth the $200 price of admission to me.