DId you get that paperwork from the IRS about purchasing? over $600.00

So who pays the taxes, buyer or seller?

Seller; that's the person with (potential) income.  If I sell something here and don't have a record of what I paid for it, I'm unlikely to accept PayPal.

recapping what's already been posted:  The IRS is after income and not imposing a "Sales Tax."  So keep note of what you paid for it (like stock transactions) and profit (income).  If you sold it for $1000 but paid $1200; that's a $200 loss, no income tax.

As for Sales Tax that may apply depending upon State/Local, but I doubt locals can track online sales yet.  In both cases the seller pays Income Tax or Sales Tax if any.

(Not an advisor, just by take) 😉

If you regularly sell stuff (audio and other) I would suggest a business ID and checking account for all transactions.  That way you could write-off all your audio subscriptions, audio conferences, travel, equipment you buy/sell as inventory plus travel, vehicle transport, heath care and other qualified expenses.  See an advisor for how and what's allowable. 

@socalml528 Revenue agencies generally look with great skepticism at claimed "business expenses".  The test of a legitimate business is the expectation of earning a profit.  Trying to write off expenses that exceed any profit earned is just asking for an audit.  I have to guess that 99.9% of the members on these sites, when actually selling anything, are doing it at a loss.  Keep all your original receipts for insurance and the tax department on the off chance you are ever asking to prove are not earning taxable income.  Mostly this appears to be a tempest in a teapot.