the company says that as the prime ecosystem haspa ed, so too have amazon's costs. >> the value of prime to customers has never been greater. and the cost is ao high. as we pointed out, especially with shipping options and digital benefits. continue to see a rise in costs. >> the last time amazon raised the price of its prime membership was back in 2014 when 20 million items were available for two-day free shipping. today there are more than 100 million eligible products as well as two-hour free whole foods grocery delivery in ten cities and a hugelyxpded digital library of music and video content. >>> analysts like mark mahaney aren't worried. he points out the extra revenue will allow amazon t inves even more back into the business. >> and you put in a $20 price increase on 100 millionsu cribers, that's $2 billion in incremental revenue cash flow that could dropdown. knowing amazon, they won't allow it to drop down. they'll invest it in something. but still it's great profit potential. >> but the stakes are high revenue from prime memberships is part of one of the gr fastesing business