..... off ebay for $10

Impossible - eBay don't sell things

or
..... off ebay for around $10

same, see above....

or
..... off ebay for approx $10

Like, I've already told you twice - what is is you, like don't understand? 

I bought the item FROM an eBay seller

or

I found the item for sale on eBay for XX$'s

 

My pet hate is "I brought it from Gary"