It's a lot of work, I'll give you that as I've done it myself, but lets break it down;
Lets say we use the UK minimum wage of £5.80 an hour, then double it just because, and then assume each case to require 8 hours of work (Mine took 4 hours to completely disassemble, cut a new hole in the back, remove all the plastic and adhesive crap -- admittedly I didn't remove any ferrous metal -- and then reassemble back after milling a fan mount out of the rear tray) ... round it up, call it £93 on top of a case that lets say you wrenched from a completely working powermac (Buy it now @ £75 in the UK for a working 1.6GHz single, I paid £82 for a working Dual 2GHz model). All the internals can then be sold at great profit, but for the purposes of trying to make a grossly inflated price, lets say you just bin them all. Then round it up again.
That's still only £170, with ludicrous assumptions over cost of parts, wages and time spent. (double for the most part)
To put it into perspective, my particular case, although not re-anodized, but crucially fully modified,
costearnt me £80 (sold the internals separately at a profit). This being after I added the price of a motherboard tray ($55 if you go the mountain mods route). I bought mine in pristine condition so it didn't need anodizing, nor do I want it re-anodizing as that would lose the apple logo and the original 'genuine' apple finish.
If I lived in the US, I would gladly churn out powermacs for that price, but alas, as you probably guessed, I'm from the UK.
First of all, we don't have sweat shop workers churning out hundreds of cases at minimum wage. Each case order is treated as a custom job, and we do the work ourselves. You've also left out cost of COMPLETE REMOVAL of all adhesive (it needs to effing spotless to reanodize), media blasting, refinishing, supplies, utilities, lease of facilities, gasoline for delivery and pickup. Add up all of those things you DIDN'T have to do with your case, convert that number from GBP to USD (very important), and then come back to us with what your real costs would be if you ran this business yourself.