When they say no bondo they dont mean it. For the price they quoted you they will have to at least skim coat the patches so hide the imperfections. Not that there is anythong wrong with that if done correctly. Correctly done filling can last for a VERY long time. However, very few shops will do it correctly due to the time it takes. A good chunk of the $2500 will be in the paint job. That doesnt leave many man hours or materials for the repairs.

If you want perfect, replace the rusty doors with donor rot free doors. Just pick and pull the shells and swap your stuff into them. Then its just paint work. Otherwise expect them to cut out the rotted sections, weld in new ones and skim coat bondo over the area to smooth it out. Done well can last a real long time. Done wrong on a door you will see rot bubbles in 2 years.

One this to ask them would be the welding method they plan to use. The best long term method is a butt weld. A skilled person with many hours can butt weld a patch in and finish it without bondo. Takes a LONG time that way but its like the rot never happened. However, the faster more common method is to overlap the patch by using a flanger on the patch piece. Then you can drill holes in the original sheet, fit your patch with the flanged section under the good section, and plug weld the holes. Much less time involved im making the patch area and easer to grind down and finish. Also leaves a nasty overlap thats rarely sealed from the back side and rots like crazy in no time.

Bottom line is you get what you pay for so ask lots of questions!!