Because originally all you told us was:
The first guy I called out only uses Don Young windows. His estimate says "Don Young single-hung, dual-pane vinyl windows in white, with low E glass and Argon gas." The model/series of the windows is not listed. For 5 windows (we combined two windows to go from 6 to 5), the cost would be $2,250
Now that you've added that he told you it was a 5 series, the window is more comparable to the NT Presidential.
I said he was unprofessional for the same reason you think they are unprofessional:
All of the estimates seem unprofessional to me. All hand-written with almost no details.