I'd you want to flash it there is no need for the 3820. You could get the oldest slowest possibly second handset i3 you can find for next to nothing and use it to flash the BIOS. It will still cost some more but should be a lot cheaper.
Well , 3820's go for 180 shipped , 4820k's go for about 210€ shipped , so I might send back my current mobo + cpu ( 1231V3 + asus h97 plus ) for 295 € and buy a 4820k , then contact msi so they can flash it ( probably paying ~30€ for transport ).
And the cheapest 2011 cpu that I can get is the 3820 .Also , a cooler should not be a problem.