Okay. I guess I would be annoyed if I purchased food at a dealer's, then had it brought over to me by someone expecting a tip when they were clearly not a part of the establishment (and when I fully expected to do the work of picking it up myself).

If you enjoyed the role-play up to and including giving a tip, then, well, cool. Sounds like a good time was had by all. But I can sympathize with the people who didn't want to participate to the point of paying the cosplayers for a service they neither expected nor wanted.