In theory, I love the idea of the European system of dropping baskets on ropes, but you do need two people, or some sort of old-fashioned clothes-line-on-pulleys device, re @WestRiverrat.
Or you can plan ahead.
Prepare to go shopping, by any means.
Lower empty baskets to street.
Descend stairs.
Cover baskets with pine boughs (or something) to disguise and prevent thievery.
Arrive at market,by any mode of transport. (We forgot bikes.)
Shop.
Return home, by any means.
Fill baskets with groceries, etc.
Run upstairs.
Haul baskets up.
@glacial: I yield on the taxi issue. My first apt. was in Cambridge, where everything was accessible by foot.
When I lived in NYC, it is true, that we all took taxis often. They were omnipresent and cheap.