Did you ever get a 'pro' quote? How much did you save? (Not counting labor, of course. We never do!)
I never got a quote to do a full swap out like I did. I did get a couple of quotes for replacement windows.
Renewal by Andersen was insane (and a hard sell as well). If I recall, I want to say they were around $1,500 a window. I had some other quotes in the $900 - $1000 range.
I did have a company do the large picture window with two flankers in my second floor living room. They replaced that with a 5 light bow. That one was a bit heavy for me to muscle around by myself (although they did it with just two guys working off ladders - it was pretty sketchy, but if they dropped it, its on them not me).
I used Andersen 400 series tilt-wash windows with unfinished wood interiors, except for in the laundry room and garage where I used pre-finished white interiors.
The windows were around $450 each + around $70 for the screens - So call it a savings of about $500 to $1,000 per window. I did 19 windows in my house. So it adds up.
You really cannot compare apples to apples though, because it ends up costing me more than just the window. Doing a full window requires replacing the casing around the windows, so that is going to run you extra. With a replacement they leave the casing in place. But my casing had 500+ coats of paint on it and was just a step above clamshell builders grade. So I wanted that replaced, but if you have expensive casing already, then that is something to consider.
The same thing goes for outside. If you have vinyl, then you likely have no need for siding modification. I have cement siding (except for the 4 windows I have set in brick) so that requires buying new exterior casing for the windows. But again, I wanted that detail and think it makes the house look a lot nicer.
An other factor to consider is that by doing it this way I was able to replace / inspect everything. The old windows were 100% removed and taken down to the studs / sill. The old windows were 1970s that had at some point been wrapped in aluminum and had storms attached. Some of the windows were rotting under the aluminum. All of that is now gone, and the underlying framing was all wrapped in tyvek and protecto-wrap with proper back dams before the new windows went in. Also, there is now proper insulation between the window and the framing, as opposed to the scrap of rock wool that was in most of them.
I was also able to get the finish I wanted on the inside - stained wood to match the floors. I pulled all the sashes and hardware in the garage and stained and finished everything before installing the windows (I also stain the casing before installing, and then just touch it up and apply a final coat of finish post-install)
So maybe I saved a little under $500 a window in real cash, but I also got a much better product for it.
And it was about $100 to tip the old windows at the transfer station, so there was that disposal cost as well.