Or did this buyer overbid?

I closely watched a five-card Harry Potter trading card relic lot on eBay over the past week, because it's rare to see multiple Harry Potter relic cards in a single auction. Listed below is a list of those cards, along with the average selling price for other copies of that card:

Card

Serial Numbered Average Selling Price*
Harry Potter and the Sorcerer's Stone
Authentic Cinema Film Card
309/397 $1.99
Harry Potter and the Chamber of Secrets
C2 Kenneth Branagh as Professor Gilderoy Lockhart
186/570 N/A
Harry Potter and the Half-Blood Prince
C8 Griffindor Students
 14/580 $5.59
Harry Potter and the Half-Blood Prince
C9 Dame Maggie Smith as Minerva McGonagall
119/490 $14.90
Harry Potter and the Half-Blood Prince
C14 Freddie Stroma as Cormac McLaggen
38/580 $6.64

That auction started at $19.99 and sold for $26.00 (plus shipping); as a comparison, the average selling price for four of those five cards is $29.12 (plus shipping).

I suspect that all of those cards are in Excellent/Near Mint or worse condition, because none of those cards are protected with a card sleeve, and all of those cards has multiple damaged corners.

If all of those cards were protected and in better condition -- I would have sniper bid $35; as is, I couldn't see paying more than the starting bid of $19.99.

Question: What's the most you'd have paid for that auction?

*Excluding shipping charges. Based on the available sales data on eBay as of this writing.