Joe is a (
very good) coin dealer that offers this
fine website free for all to use. That service has to be funded by
his business - which isn't thriving if he lets people come here and effectively advertise for
his competitors.
Realistically you cannot always buy from
Forum, because
Forum does not always have an example of the coin you might be trying to acquire. If this is the case, I would suggest that sites which are also widely recognized
authentication services are also a low risk proposition (generally speaking). There are lots of well respected ancient coin dealers in the world, and there are some that have difficulty finding their ethics. It's really not that difficult to ferret out who is which.
Any time I've purchased from a well-known, trusted, and established dealer - if I
had any doubts on concerns, they have taken the coins back. Perhaps ask about their policies in this regard first before
buying something impulsively? Also, as a general rule, consider purchasing only from places that specialize in
ancient coins (and that check out, and, and...).
If they also sell paintings, cars, estate jewellery, etc... you are likely not increasing your odds of purchasing an authentic coin if you aren't adept enough to authenticate it yourself