It's still too much in my opinion.
But if it is, for example, a chemical company that sells many products (not only SN), then it should be a real SN.
SN is simply salt that is cheap to produce, so no real company has any reason to cheat.
If this company only sells SN and the website looks suspicious for some reason, I would avoid it.
People usually pay a maximum of 50-100$ for 500 grams.
But you can also buy it for 10$ or even cheaper.
150$ is a lot, but if the seller is a real and reliable company, the SN should be fine.
However, if you don't need to buy yet, you can look for another place.