By the way, some might find this useful for purposes of estimating potential profits from magic find on items:
Blizzard has stated, that the way MF works is that every time an item is rolled, the game determines it's quality this way: There's a chance it will be legendary, a chance it will be rare with 6 props, chance for it to be rare with 5 props and so on, all the way to the bottom. So basically when an item is rolled, the game checks if it's a legendary - if it's not, the game checks if it's a six-prop rare, five-prop rare, and so on.
Now the rolls are random. But for the purpose of this argument, let's think of it in a slightly different way. Let's say whenever an item drops, it could be one of 6 options: a legendary, a 6 prop rare, 5prop, 4prop, 3prop or complete shit. And since it doesn't change anything, let's say all those are allready rolled for, and now the MF lottery only determines which one are we going to get. So we have to factor in the NV, our paragon levels and all the already owned MF. Basically, every point of MF under the cap (that is, every point that actually increases our MF) will increase our chance to get the better item at least a factor of 0.21 (1 divided by(100% base MF + 75 NV + 299 paragon + items MF). For the Paragon 0 and no MF items it's a bit more than 0.5.
Basically what I'm saying is that every single of MF can be estimated to increase our profits from auctioning items by anywhere from 0.2% to 0.5%. So an item with 10% Magic Find will yield an estimated 2%-5% increase in profits. Multiply this by FUCKING RNG LET ME ROLL A FUCKING JACKPOT ALREADY, and voila, you've got the estimated worth of your MF piece.
TL;DR - everything below 100-150 base MF is a really fucking good long term investment since the last paragon levels will take forever.