The most I've thrown at a model was $60.00 Canadian for Classic Airframes' 1/48 F-5A Freedom Fighter.
Put that up to $73.00 after I put out for the Leading Edge Decal sheet and resin IFR probe to go with her.
Other mentions (all in Canadian funds):
Hasegawa 1/72 F-111G RAAF Aardvark ($50.00)
Warhammer Eldar Falcon Grav Tank ($60.00)
Babylon 5 Wars white metal Vorlon Battle Cruiser ($40.00)
Best deal I ever got on a kit was:
Revell 1/144 Space Shuttle ($1.00)
Yes, ONE Canadian dollar! The toy shop at the local mall got an overstock of them and had to get rid of them. In hindsight, I should have bought all five.