Lots of people from Czechia use alza.cz for purchasing electronics and computer stuff. Surprisingly it also ships to many Europe countries and have English site at https://www.alzashop.com/ . It doesn't list as huge variety of items but offers quite nice filtering, categorization, reviews, etc. I personally use it more often than Amazon. What forces people to use Amazon? Laziness? There are also price comparison websites which people can use to compare sellers... I never really understood why so many people buy through Amazon.

Important considerations. Also regarding the power of scale, I think people are happy to go straight to Amazon instead of shopping around because they're confident the price they get is going to be at least as good as anyone else.

So consider my proposal to add to the lexicon of common market regulations: Same Price for All. You can't charge one customer any different unit price than another. (You can add a flat transaction/processing cost and maybe price-proportional fraud-insurance fee.) Volume, customer non grata, negotiated deals...nothing changes the advertised price.

Believe me, I'm one of the most laissez-faire people you're going to meet. But I think this ends up being healthy for all for the same reasons that other anti-monopoly laws do.

You just described Fair-trade laws[0] enacted during Great Depression and repealed around ~1971. Matt Stoller also described these laws in his book.

[0] https://www.britannica.com/topic/fair-trade-law