I don’t think that the gift in itself is a problem or that your son should return it, however I would talk to your son about a power imbalance and make sure that his friend isn’t asking for anything in return or manipulating him. Expensive gifts that have to be paid back is a tactic that gangs (allegedly) use to recruit people but if they are really best friends then I wouldn’t be worried.
I don’t think that the gift in itself is a problem or that your son should return it, however I would talk to your son about a power imbalance and make sure that his friend isn’t asking for anything in return or manipulating him. Expensive gifts that have to be paid back is a tactic that gangs (allegedly) use to recruit people but if they are really best friends then I wouldn’t be worried.