it may however be worth trying to find out what this sold for:

https://backpack.tf/profiles/76561198123378599#!/compare/1563494400/1563840000

It is not unlikely it was sold for less than he paid himself, making 90 flat look high (especially seeing how it also went to and from a bot (the other trade in your suggestion + its resale))

Discussed this with the other moderators too:

Even without confirmation, it is very likely it was sold for less than 90 there. Along with the two sales to and from the bot, that makes for 4 lower sales (or 3 without the unconfirmed sale) vs 2 higher sales, and one of the 90's is very likely one that resold for less. The evidence for 90 flat is too weak here, and I believe waiting for more sales here and leaving this outdated is the best way to go.