What kind of double hung window are you using

A - Vinyl replacement

B - New complete unit

This needs to be answered before anyone can presume to give you any sort of guess

It would be important to provide information on the house details/specifications regarding exterior and interior wall finishes. An example would be wood siding with wood casing at the exterior with plaster and wood casing at the interior. This example would provide a less expensive installation. The opposite might involve a stone exterior mortared to the existing window frame with plaster returns into the wood jambs at the interior. The house details/specifications are relevant when installing a complete new window, and not the "replacement" style of window that is often mentioned on this forum.

I am looking to install a complete new window, not a "replacement", and the exterior of my house is clapboard.

I really don't see how anyone can answer this question without seeing the job. knowing what window you plan on installing as well as a host of other issues such as;

1. You will pay more for labor per window on just 2 windows than you will on 15-20. In fact many good installers wouldn't even entertain installing just 2 windows.

2. The area of the country you live in. Labor rates can vary considerably.

3. The experience of the person doing the work. Some hack who's been fired from his last 3 jobs is going to offer to do the work at a cut rate price because he can't get a job anywhere else. OTOH someone very experienced with a good reputation for attention to detail is going to cost you more because he's proprly licensed, carries insurance and has overhead. He's also likely going to give a decent labor warranty and actually show up if you have any problems.

Why don't you contact a few installers and ask them if they are interested in installing just 2 windows? If they are, have them come by, look at the job, explain what they will do and then you will have some basis other than price to decide what the best value is.