Well i never buy the games when theyre expensive and never buy them in the release date...
But the most expensive game i bought was back in the ps2 days.
I still remember it "Jak3" for the playstation 2. I loved the fact you could use Light and darkness powers, and fell in love by the Steampunkish look of the game. In those days off course i was only a kid and my city didnt have any gaming store. So i ran from my city to the next one in hopes of finding the game, and ran back before my parents arrived. When my parents asked me where i bought that game i would say it was a demo that came with a magazine (i still have that demo has well xD).
Costed me 35? the equivalent to 49Dollars i think. i got home all sweaty from the running, almost got mugged and had to go trough a kinda dangerous path. For a game xD ... well what can i say i was a kid back then...
The second game was Pokemon Yellow, back when i was a brat... the last game my parents ever bought me (they bought me pokemon blue years before has well). Costed them 25?... it was a week after the release date has well... i think thats 35Dollars...
The third "most expensive" game would be Orange Box 20? = 25Dollars i think... tottaly worth it....
*edit*
I forgot about the Guild Wars game... 40Euros = 56 Dollars for Prophecies and Eye of the North. THAT was my most expensive game... also worth it. A friend recommended prophecies to me along time ago so i ended buying the prophecies+EoTN pack. That game made me love the GW universe and Lore and made me buy Factions and Nightfall in the following years. Still have them to this day and love them.
The whole deal is rounded to 85Euros = 120Dollars... not a bad deal if i may say so... xD