[Draenin]

RoW has been at 500 diamonds since alchemy. You're like a year or two behind the change. Before alchemy, they were usually 300, but that's when diamonds used to be 300 as well.

Also, resetting will not give platinum and diamonds their original value back. Right now, 500 plat per diamond is ideal, mainly because it is easy to calculate. If you want to buy a gold key, it's 20 diamonds or 10,000 plat. With the price of diamonds set as what it is now, nearly everything has a stable price, rather than an estimated one. (Except rare items, but as much as you whine, their values will always be up to the seller's discretion.)