Rebbys whiskers
 

I was wondering how much a stack of them are worth?

Im not sure how useful they are in terms of handing in for faction - might be worth something to a factioneer trying to max everything but I dont think the appeal is too wide.

The quest gives such little faction it's not worth the time.

I ended up selling two stacks for 75 plat, and the guy who bought it said he got enough faction to use the bank

It's +10 for Coalition of Tradefolk/Coalition of Tradefolk Underground per turn-in. That's the majority of Freeport merchants/bankers and the Thieves guild.

+200 faction a stack is quite good. It's the Carson McCabe/Freeport Militia/Corrupt Qeynos Guards portion that is little (+1 per turn in)

For banking in Freeport Tonics for Groflah (Tumpy Tonics) are far superior since they give the same +10 faction to the Coalitions but also +10 to Knights of Truth who guard the bank... as well as +7 for Merchants of Qeynos as a bonus.