As of patch 2.0.x, you get 75 rep points per turn in.

Friendly to Honored (6000 pts) = 80 stacks
Honored to Revered (12000 pts) = 160 stacks
Revered to Exalted (21000 pts) = 280 stacks

Here is a list of what you get when you do the hand ins.

A Donation of Wool = 60x Wool Cloth (at lvl 50 you get 400 xp and 350 Thunder Bluff Rep).

A Donation of Silk = 60x Silk Cloth (at lvl 50 you get 1000 xp and 350 Thunder Bluff Rep).

A Donation of Mageweave = 60x Mageweave Cloth (at lvl 50 you get 2000 xp and 350 Thunder Bluff Rep).

A Donation of Runecloth = 60x Runecloth Cloth (at lvl 50 you get 3950 xp and 350 Thunder Bluff Rep).

Additional Runecloth = 20x Runecloth Cloth (at lvl 50 you get 75 Thunder Bluff Rep).

@Lvl60

Donation of Wool [60] (+150 Faction)
Donation of Silk [60] (+150 Faction)
Donation of Mageweave [60] (+150 Faction)
Donation of Runecloth [60] (+150 Faction)

Additional Runecloth [20] (+50 Faction)
( Additional Runecloth [60] (+150 Faction) )

That's correct, it's 75 rep per turn in. Turn in a stack and you get 75 rep.

Let's say you wanted to get exalted from 0/6000 friendly. You would need exactly 39,000 reputation points (6000 till honored, 12000 till revered, and then 21000 till exalted)

If it's 75 rep per stack, or per 20 Runecloth, then 39,000 divided by 75 is 520.
You need to turn in this quest 520 times to get from 0/6000 friendly to attain exalted.

Which means, go farm yourself 10,400 Runecloth!

For humans, of course this is much easier because they get 10% more reputation points than you would regularly.

If you're a human you get 82 rep per turn in (82.5 to be exact).
So if you wanted to get from 0/6000 friendly to exalted AS A HUMAN... You need to turn in this quest only 472 times (472.7 if you wanted to be exact). Which = 9454 Runecloth.

simple math, good luck