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 equivalency at 13 trips a year. So, Prime is cheaper if you grocery shop more than about once a month. I certainly do.
This assumes the groceries are the same price. Unfortunately, Amazon Fresh prices are likely higher (for now). I did some price comparison with Safeway after placing a Fresh order sometime in 2012. Amazon prices were higher on every item except one. In some cases, Amazon was nearly twice as expensive.
I'd be really interested to see this in Boston as well. I can walk to grocery stores easily, but for heavy/bulk items like drinks and chips, I'd much rather pay to have them delivered. I already have iced tea delivered from Amazon, but the selection is just okay.
My experience with Peapod is a few years back when I had a broken foot and was on crutches. It was great for me in those circumstances. I could order from a (somewhat limited) set of things and they would (mostly) arrive at the scheduled time. Going to the store to pick up the odd item wasn't that big a deal but doing a full grocery shopping was difficult.
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.)
I can generally make the entire trip in just under an hour (sample size: two out of three), but I'm blessed with twin advantages of being unusually efficient in Trader Joe's and having a ZipCar lot literally across the street from my building.
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 equivalency at 13 trips a year. So, Prime is cheaper if you grocery shop more than about once a month. I certainly do.
If they bring this to Boston, I'm in.