Well you have a point... In a way as an investment- the car paid off quite well for the city as over 7000 tickets were sold for the unveling alone, so the $$ value return to Tulsa was huge on this hulk.
I cannot help however in thinking that the idea of burying the car the way they did was somewhat of a joke on us here (in this time) as the construction of underground facilities was quite well known especially after the second world war and even later in the late '50's where the "fall-out shelter" was then the "must have" item for your home.
IMO They clearly knew what they wanted to survive (the time capsule) and took steps to insure the contents did.
What remained for publicity (the car) was essentially two things: A short term boost for the local Plymouth Dealer back in 1957 and what turned out to be a long term promotional product test of grease, bags, plastic and a mylar coating film in an environment that they knew at best would have been very damp - and likely flooded for the better part of 50 years.
I feel bad for all the folks who actually believed that the bag was going to hold and the car was going to reappear looking like it went in.
