Gems don't seem to have depreciated as badly as other mats and it's fairly consistent since even if you don't get superiors fine gems are still good money.
So run Nif as much as possible.
Kind of curious here, who do you see buying fine gems? A decent party can clear Zecallion in 5 mins or less, and most players that I have seen just use one fine gem per slot and refuse to try for higher rolls because "it doesn't make much difference anyway". I just can't see anyone going nuts buying fine gems trying to get a max roll on a bracelet when they can run Zecallion to get their own gems. Throwing like 10 fine gems at a bracelet is only going to net you about 50 more ATT above average anyway. If you have spare fine gems and nothing better to use them for, sure, go ahead and gamble to get a max roll, but actually spending tons of gold buying fine gems off the market to do it...there's probably very few people willing to do that.