Considering that site shows GTA 1 and 2 as costing £20 it is perhaps not the most reliable way to calculate your account costs.
But I like showing off my epeen as much as the next internet resident, so it found 187 games, worth £1796.63 GBP.
In actuality, I expect I've spent somewhere nearer £200, maybe less (since 2005), thanks to steam sales.