Not sure of your point. Did you make money buying and selling equipment here and on Audiomart? If so, it's income. You don't have to fight the IRS; just tell them the truth, pay up, and move on. They'll be very accommodating.
( If you 'lost' money, like most of us have [e.g., you spent money on equipment, which you own, or sold it at a loss], then it's a hobby, and those losses are of course not deductible. )
( If you 'lost' money, like most of us have [e.g., you spent money on equipment, which you own, or sold it at a loss], then it's a hobby, and those losses are of course not deductible. )