I don't think being a business makes a difference. And it gets worse.
Based on my understanding of the the tax code, if you're a business and buy an item for $300 and sell it for $299, you get a $1 tax deduction...or somehow can use that $1 loss to your advantage. But if you're an individual and conduct the same transaction, you can't take advantage of that $1 loss.
Whether you're a business or individual taxpayer, if you buy an item for $300 and sell it for $600, you're supposed to pay taxes on that $300 income. As a business, you'll keep careful records of the cost basis of that item, so you can easily explain to the IRS that your taxable income is $300 and not $600. Many individuals won't have those records, so they'll have to pay taxes on the $600 in "income," even though what's taxable is only $300.
I've heard anecdotally that for small, limited transactions, you can just write in certain amounts on the proper form and it will be enough. For example, that you paid $300 for something, but sold it for $299, so you lost money on the sale. But I'm sure there comes a point where the IRS won't be ok with just seeing a number inside a small box on a form and will want an actual receipt. And when the IRS wants a receipt, the audit process begins.
Also, even if this anecdotal information is true, what if you use Paypal for many other transactions, such as selling old rockets on message boards, FB marketplace sales, getting paid from a freelance client, etc. All the IRS sees is a giant dollar amount. The onus is on you to parse out every. single. transaction. to explain what is and isn't taxable. And if taxable, what the cost basis is, so you can prove what's actually taxable income.
So, who wants to play tax roulette with the IRS, where winning equals not paying taxes you don't owe and losing equals getting audited?