Matchbook Fees

[thing85]

Okay, I'm trying to figure something out. I just placed an arb using Matchbook (and SIA, but that part doesn't matter) of about 1.7%.

I just realized that Matchbook charged a 2.9% fee on my NETeller deposit ($14.50 on a deposit of $500) with a note, "to be applied as Commission Credits." I'm just trying to figure out how all of this affects my arbing when I use Matchbook.

If there's a 2.9% fee on Matchbook, does that mean I need at least a 1.45% arb when using Matchbook (since the 2.9% fee is only on one side of the arb)?

If anyone can help me make some sense of this, I'd appreciate it.

Thanks.