You can at the build shop near spawn, it is right next to the giant Rubik's Cube and sells all sorts of blocks. If you have tp, you can use /warp shopbuild.
Actually, I would like a command where you can buy items wherever you are. Would be great for building and such. /buy <itemname> <amount>
I'm not sure, but I think that the price you would buy with the command would be the same as the /sell price and the prices for blocks at the server shops are set at more than the /sell price.
No I think that the server shouldn't sell any items and make economy entirely based on players Buying something from server sets a max price on a item
or, set the price as the same as spawn store, and then that would just make it more convenient for users. Maybe charge a little extra for that reason.
Set a home in the spawnstore and your problem is fixed, having /buy would discourage people from buying from other people's shops.
If it is the same as the spawn shop (portable spawnshop through commands) then how is it any more discouraging than the current spawnshop?