80 cents?
.. more like AU $1.60 around here ..
All your assumptions are as reasonable as all of those of SETI - no more, no less. At the very least you would have to show that our solar system is, or was, rare in this galaxy, in some way that is valuable to other civilizations which would then want to visit our little corner. We still don't know enough to be able to say that. And also, just like SETI, you're assuming sentience and technologies along anthromorphic lines, which may or may well not be the case.