Amazon is actively using their data collection on sales to determine where to get into the market, putting other sellers and manufacturers out of business. This isn't what I'd call "fair". I don't believe this is illegal but it certainly seems it should be.
It's totally fair. If you can't differentiate against a retailer's house brand, you don't really deserve to be in business (I say this as a business owner that competes against Amazon's house brand).
Amazon has enchanted the world with their “prime” badge. Enchantments rarely end in the enchantee’s best interest.