That's like saying, it's not raining, but there's water falling from the sky. If the cowl leaks there's rust.Owner says pretty solid, no cancer rust but has cowl leak.
It is inexpensive if you do the work yourself; but as you indicated it is time consuming. For the owner to pay someone else to do it, the job is expensive!The cowl area is most certainly rusted, but I have to disagree with the repair being "very expensive". It's time consuming (about the same as hanging a new rear quarter), but the actual material cost is minimal. The '66 I posted earlier has all new cowl panels installed.