The bottom line here I think is this is a bike with limited appeal to any vintage collectors as it is very low-end. Therefore, the value is going to be as a rider, basic transportation, as described by seypat.
The last maintenance was so long ago that it is obsolete at this point. The tires may or may not last, and the buyer will likely need to replace fairly quickly. Tubes probably will be OK, if they were in good shape last time it was ridden. That's based on my experience, this bike may not follow that expectation.
I'd put it on the local Craigslist at $150.00 and be ready to take offers.