Need help determining the value of these very rare Eli Manning cards

[Ericc5Bears]

So my close friend is looking to unload some of his old Eli Manning collection and since I'm into cards much more than him nowadays (mostly basketball though unfortunately) he's asked for my help. I was able to give him an estimate for most of his stuff just via regular ebay/PWCC comps but then he showed me something pretty crazy. He has 4 of these '04 UD signature sensations cards which are hand-numbered to 10. I couldn't find any sales within the last 8 years (which makes sense since 40% of them are in this room lol) and even trying to find comps of comparable players (Big Ben, Rivers, etc.) didn't yield much either. He really wants to get a solid idea of their value before he decides to sell or not so I was hoping for some help from some of you guys more familiar with football. Any info is greatly appreciated, thanks guys.

PIC: https://imgur.com/a/1rcTrqa

[seanob22]

These are cool! Looking at the checklist it looks like each signee had cards numbered to their jersey number (ie. Peyton was out of 18, TB out of 12 etc). Looks like a Brady BGS9/10 went just over $1000 back in October and there are a couple of Rivers up with a $200-250 BIN on eBay. I'd put these in the $500-600 range each.