Well, I dont understand your issues on costs. Cost in running a retail store are much more and overheads are more, inventory costs are more etc. Whereas you can manage with much lesser on each of the above.
As for what neighborhood stores deliver these days, a grocer is willing to even deliver me even a lose cigarette these days, just to make a point on service.
As a consumer I am not willing to pay the same price to you as retail price, while also increasing my RISK and delayed gratification.
I think sellers here need to start thinking of why would anyone buy from them. And a gurantee is something that everyone gives, it cant be the justification for your inflated margins.
Unless you are just another retalier... Then I have nothing to say but to go to the closest store and pickup the good, see if it not broken and owrks properly, pay in cash, and walk home with the product safely in my pocket.