Although I have never yet paid for someone to come and spray I did talk this over with the local NRCS office just last week. He said that an average per acre cost to spray Roundup would be around $14.80. True or false, I do not know, but that is what he said.
Maybe the person you asked had a minimum charge or something, it may not be worth his time to spray 2 acres. For 2 acres you may be able to spray that yourself with a hand sprayer. I would guess that you could get that done in a couple of hours.