Realistic. Friends don’t ask you to pay top dollar for a vehicle with glaring, possibly expensive-to-fix problems.
If he is a gear head or knowledgeable car guy, then this is 100% true.
If he knows or cares nothing about cars, he may simply be listening to his good ole boy mechanic who isn't bothered by things like this and tells him 'its no big deal for now' and 'we can fix it later and cheaply, if we ever need to'. If you believe this to be the case, I would recommend getting the Lexus dealer to deliver the sanity check. "I love the truck but am a little suspicious of what your mechanic is telling you. I will pay asking price if we can agree that you'll have Lexus return this to a clean bill of health first."
Or, he simply may be one of those people who consider a bucket the permanent solution to a roof leak and undercoating to be an accepted structural replacement for rusted metal. I wouldn't buy a car from that guy at almost any price.