Think of Amazon and how their changes their prices every few minutes, only the other week I ordered something then it dropped $5. I'm not entitled to compensation. And its not a lottery, the price you see is the price you pay should you choose to buy. Customers were complaining the price was too high, and so it was lowered. If we all tried to set a price at once or kept it level or moved it up and down willy nilly then we'd get nowhere. 467,149 cooks spoil the broth.
Last week demonstrated the Bitmain price to be a lottery for sure, the variable being which day/hour you purchase!
I've ordered many an item from Amazon, and the price variation is very small, though admittedly fun to shoot for the low. $50 out of $420 isn't small! Multiply by two and it's a major hit. Purchase by any other means at any mainstreet store, and you'd receive a refund for the difference! Of course, by your opinion, Bitmain should be exempt (must be nice to have your financial resources).