Why did Mab?

While re-reading Small Favor I noticed something I had previously missed. During the conversation where Mab asks Harry to find Marcone, while Harry has the water in his eyes frozen, Mab kisses his ear. Why?

The best potential reasons I can think of are:

1: because Mab took Harry's blasting rod and memories she had to give something in return.

2: Mab gave information to Harry about Marcone and thus needed to extract a price from Harry which took the form of ear kisses.

Neither reason is particularly good in my opinion. They both seem to be in violation of fae bargaining (the trade does no seem equal nor did Harry agree to anything as far as I can tell) but I can't think of anything better.

Does anyone have an idea why?