Earlier quoted context omitted.
Back of the napkin calculations put the cost of Prime Fresh at less than the cost of Zipcar grocery shopping. Realistically, you can't drive to the grocery store, do your shopping, drive home, unload the car, and drive the Zipcar back to its parking spot in anything less than two hours. (And maybe fill it up with gas, if you're unlucky.) Even with a cheap Zipcar, that's $16 + tax per trip. $220/$17 puts the equivalen…
I saw ads for stop & shop's "peapod" service on the T: http://www.peapod.com/ . Haven't used them myself though. (and the ad said that you can use T2013 as a coupon code and get ?15$? off your first order)
Now, if I could reliably do a full grocery shopping with all the ordered items delivered from a good selection I might be tempted. But probably wouldn't pay the necessary fee as the grocery store is 4 miles down the road from my house and I have a car. (Also I imagine I'm too far out of the city to get the service anyway.)