Very interesting point you raise mate. It's weird, as it almost makes it sound as if we've been lavished when we all know the truth is far from it. My guess is when you spent huge amounts on players its very hard to top it even with inflation, whereas we are kind of incrementally increasing by small amounts. I can't see the likes of these amounts (off the top of my head, don't know if they're accurate/up to date) being beaten;
Villa £24 million Bent
Chelsea £50 million Torres
United £34 million Berbatov
Spurs £22 million Modric (they'll beat that soon)
Arsenal will surely break theirs soon.
Honestly, I can't see us spending over £15 million in the foreseeable future. Not before (big) sales.