On my small server, they range 500-800G. A sale run usually nets anywhere from 75-100K depending on buyers. Probably about 115 runes? Enough for a week easily.
The bigger issue is our economy doesn't even have close to that number of runes for sale.
The benefit they provide is minuscule. If you don't want to pay for it, you will barely be losing anything.
If you want to be the absolute bleeding edge, that's the price you need to pay.
Play tank class, get weak aura to tell you when tank or dps are needed for LFR or heroic dungeon. Queue get bonus item.........Profit.
Yeah, but even on Cenarius, you can spend the first ten pulls figuring out healer cooldown rotations, positioning, wisp detonations, etc, before you really need to use the runes. Cenarius is a bit different too, in that you can reset him without a wipe - lose two people early? Just reset him by having the drake tank run into the water, and you've just saved the raid eighteen runes. Something like Il'gynoth, where it's still a dps check at the end, you can save runes until you're hitting enrage in the second heart phase, since before that it's about optimizing damage and strategy more than a marginal increase in primary stats.
I sell those for money, don't really see the point using. I forecast an infinite rune item with hefty price anytime in future.
Bigger question is when will we see a unlimited rune again like we had at the end of WoD?
We're almost 5/7 m mythic and nobody uses them in our guild. I'm waiting for a reusable one like we got in 6.2
If you're so hardcore you should have plenty of gold from carries to just buy them off the AH