I know, I know, it's the principle of the thing, but really guys.
If you did not have a written or otherwise enforceable documentation of the business sale,
$3000 or $3 dollars, both of you were being a bit careless. Are both of you 15 years old and this is your first business transaction? No? Then abide with the consequences of the risks that you took in entering a transaction for an intangible good [service] where there is possibly little or no real possibility of financial recovery from a breach of the contract. If there are real claims of a failed business deal, find a proper forum, away from your general customer base, to resolve any issues or hurt feelings.
Although this train wreck has been fun to "watch", it can't be good business practice to be sniping at each other publically.
Me, as a customer, I'll buy from whomever I care to.
Remember gentlemen, you're not selling food or shelter, only the goodwill and enjoyment of participation in a Gentleman's [or Lady's] hobby.

Steve Gobel