It's a near certainty that Amazon will lower prices at Whole Foods (by accepting lower margins and targeting faster growth and expansion), so if anything, it'll improve affordability.
Delivery costs are a real issue, but I have a hope that we will get self-driving trucks in the near future and delivery prices will fall.
The kinds of foods needed in those areas are fresh, cheap, high spoliage items aka unprofitable to touch unless in bulk.
That is, by lower quality standards and working conditions.
If its own internal (non technical) sectors are to be taken as any indication.
If Whole Foods is currently getting a 10% margin on a product and Amazon says we'll sell it for a 5% margin, nothing else has changed in the store or the product, but the price and margin are lower.