I agree with this premise about pricing.
I'm also a target customer and in fact I tried out Amazon Fresh.
I am mid 20's, upper-middle-class, living in Santa Monica(Fresh delivers here) and I chose to not keep the membership at $220 because it was too steep.
The service itself is awesome and I thought maybe the best part is that when they delivered refrigerated food they used frozen water bottles and encouraged us to keep those waters even though we had not ordered them because it was less trouble for them to collect them every time.
Overall I was pleased with the service itself, however at $220/year its a bit more than I can justify for strictly a convenience fee.
I've been a prime member since 2010 and order almost everything off of Amazon, but I'm all to happy to walk/drive to the grocery store to pay the same prices or slightly less than Amazon Fresh.
Also even though I now live in Santa Monica I still have two cars which is probably abnormal, that said even if I did not have a vehicle (I RARELY drive here) I could not see myself finding the $220 per year "worth" it to me