guy had 58 keys, probably got some after the trade but you can't tell how many, better adding him and asking yourself

You need to check the history of the currency before assuming it sold for said keys. I did the checking for you and came up with 23 keys which based on the then price of buds (13 keys) works out to ~1.8, a far cry from 2.5 buds. Sort by time, its the keys between the xeno set and the basher and crate. http://backpack.tf/profiles/76561198120552341?time=1418371200