I'm willing to take the chance that pyrite doesn't get prospected into epic gems. But assuming it does what do you think is a good cost to start stockpiling it now? I know it will vary from server to server but a good general price should do.
It is hard to say since we don't know what the chance of prospecting an epic gem will be and how much they will go for exactly. Say there is a 10% chance you can get an epic gem from each prospect and the gems will sell on average for like 500g. At the moment i have 75 stacks of pyrite, which equals to 300 prospects. 10% of 300 is 30 and multiplied by 300 would be 15000. Just say you can make 5000g off the rest of what you prospect, being 1/3 of what I could make off all the epic gems. Thats around 20k gold total. 20k divided by the total number of pyrite i have is 8. So I'd need to be buying pyrite at 13g a piece to make it break even. I have never paid more than 160g for a stack though so if it works out atleast this way then I will make out alright.
This is all just guessing the variables though. All my math is pure speculation and I took a break from the game for awhile so I wouldn't say its speculation at its best either. Early in the patch they will likely go for a bit, maybe up to 600-800g on some servers. This is just going off inferno cuts being around 200g on my server. The price will be dependent on how many people are trying to prepare for it though and you have to consider how much honor/jp they may cost.
Its honestly up to you to decide how much you think is worth risking. Like I said I bought all my stacks back when they were 160g or less though so I'm thinking if its looking like a bad investment to prospect then I can sell the stacks for quite a bit more at this point.
Yeah, it's a big risk. If pyrite doesn't prospect into epic gems then it will essentially be worthless, but investing in something safe is no fun! On my server the price is like 60-120g per stack. I usually buy it if it's in the 60-80g range, so 3-4g per ore. You should also check the price of pyrium bars. On my server the bars are like 12-14g, that's 50-130% profit for smelting :P I sell as much as I can in the form of bars, but I buy way more ore than I sell bars. Don't go overboard in smelting though, the price of bars should drop when the truegold price drops.