Matching hobby income with 1099-k from paypal

It seems that there is a lot of confusion on that point.  I have a knife collecting hobby that got way out of hand this year...gave me something fun to do during covid.   I typically purchase and resell knives...typically at a loss but a few at a large profit.  So in the end I have made a slight profit, around $300 or so.   So in my instance, if I have $10,000 in sales but the cost of those goods sold to my was $9700, I claim the hobby income off $300?   

 

The TCJA says hobby expenses are not deductible.   I assume that this means paypal fees, shipping, etc are not deductible, but to calculate hobby income received I can still take sales - the cost of the goods sold?  

 

In addition, I sold some old personal property which I don't have receipts for and just want to zero those out.  I sold them for much less than they were worth.

 

With these, how do you square it up with a 1099-K?