The most expensive one that I have is probably my MiuMiu. But it was a present so I dont know price. I bought myself a gucci bag for 800 CHF (thats about 650 $). my first and most expensive designerbag-purchase.
My Gucci was a gift, but I can't recall the price anyway, though it was on sale.
The most expensive bag I've bought myself is 164$, Vivienne Westwood bowling bag on sale from 500-600$. I've only gotten into bags recently though, so I'm sure it's only going to get worse from here. I'm saving for a 500$ one which I'll be able to get in the next week or so. ;P