Despite the expansion announced Tuesday, Amazon likely understands that it could take a few years to know if it will scale, according to Rick Watson, founder and CEO of RMW Commerce Consulting.

“At the end of the day, it’s not going to be meaningful for some time, because this is such a small program,” Watson said by phone. “There’s something like a thousand sellers every day that joined the Amazon marketplace last year. How many are going to join with Buy with Prime every day this year? Not nearly that many.”

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