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.