Different countries use different money, and also if they sell in the place then it can still be a price for the different place, which does not necessarily involve surveillance, nor does it necessarily involve hidden fees, etc.

(If they try to prevent someone from buying them and using them elsewhere or buying one for a specific other person who requested it who they do not know, then that is different, but it might lead to different issues (e.g. liability of tampering with medications, different regulations in different countries, etc).)