If we're talking about just doing the hobby... $20,000-$30,000 maybe. This is mostly due to computer equipment purchases and upgrades over a 12 year period. AMVs certainly increased my interest in computers and the majority of my upgrades in the past were attributed to it. While I can't say my most recent, and most expensive, upgrade was done because of AMVs, it was something I planned for non-the less and I use it for editing a lot more then I've used it for 3D rendering. And then of course my anime collection which, after doing a rough calculation, might have cost me upwards of $2,000 - $3,000 or more. Normally I might exclude some titles from that list but I attribute my interest and purchase of anime because of the hobby.
If I add in cons... with airfare, hotel, registration, and spending money (food, gas, etc.), doing a rough estimate, it's $10,000+. Most of that is for airfare. Granted, i usually don't go just for the AMVs but to see friends. That said, I wouldn't have said friends if it wasn't for the hobby, so I'll add it in because it make the number bigger
Sooooooo.... Over the course of 12 years this hobby has cost me upwards of $40,000... I think it's time to retire >.>