I, for one, would think $1900 for an International DTAxxx with a pre-electronic engine and a stick would be worth it. The first automatic transmission rebuild that I did NOT have to pay for would make up for a couple of hundred extra on the purchase. A clutch replacement if needed I could probably wrangle myself, though the truck transmission is sure to be heavier than the Chrysler and Mitsubishi units I have wrestled in the past.
The rust (in the photographs) does not look too bad for a northern states bus. The back door has some rust streaming out from under the window rubbers, where the rubbers have worn through the paint. In comparison, the back doors of 20-year old Bluebirds around here look like the rust from the hinges was applied to the doors with a paint gun. Some of the Bluebird hinges look so rusty you would think the back doors wouldn't open with a crowbar.
The rust around the tires appears to be where pebbles thrown up made pinholes in the paint. I don't think it's too late to catch any of this. Without seeing the bus myself, I would tend to believe the rust is cosmetic, but with the potential to become structural if allowed to proceed unchecked.
The only rust that really worries me is the inside panel next to the rear door:
This makes me worry about what is under the rubber floor. A few of the buses on Skoolie,net had some floor repairs in that area before conversion. What I would check if I went to see it, would be opening the back door and seeing if the floor was soft in that area.
On the plus side, you don't have to remove the warning lights, nor paint it non-yellow within 14 days (where required). I don't know if you asked the owner to come down in price without looking at it. I would think it would be worth a closer look, and if you still feel the price is too high, leave an offer. If you looked at it, and then informed him that x, y, or z made it worth n less to you, and said "Call me if you want to sell it for (my price)," it just might work out.