In Spain, Marijuana is Legal, but selling it is illegal. There is a loophole in the law, there are many Associations, or growers clubs in most large cities. You join these clubs which are like a co-op, and instead of "buying" they call it donating to the operation. The prices vary depending on the club. The pictures are a club in Barcelona which is mainly for tourists, so the prices were the highest I had seen anywhere in Europe(15-25/gram). They did have a huge selection, and also a lot of concentrates.
The best prices I found in Barcelona at an Association were 6-10/gram. This was at a smaller club that was used more by locals than tourists.
You probably already know that it is illegal to sell or buy weed on the street in Barcelona. For tourists, the best way to do this is to join a local cannabis club. Visit https://barcelonaweedmap.com/ to learn more. This is the only option if you want to enjoy marijuana legally and to a high standard. I myself have been visiting it for about two years now, and I'm really glad I chose them.