Amazon extracts a lot of the value of a purchase from the seller's take. Sellers risk sanctions if they sell a product cheaper thru their brand website.

It's normal for wholesale prices being at 50% to 60% of what the retailer will sell it for. It's always been like that.

And those wholesalers would not do business with you if you undercut their retail price.

Amazon's practice is normal throughout the industry.

I know this because my business in the 80s would wholesale my products through mail order retailers.