You wanted to know why there aren't all time lows on other stores. You agree that the lower the price gets the more people are likely to purchase it. But then you think userbase is irrelevant?

Let's say there are 10 million gamers in the entire world, 90% use steam 10% use Epic. Not that it matters but I'll add it anyway to further prove the point, Epic takes 10% and Steam takes 30%. You make a game that 50% of all the gamers in the world want to buy at a certain price. Let's say you have no issues selling on Epic and you sell at full price ($60) to the 50% of Epic customers. You make $60 * 0.9 * 1 mil * 0.5 = $27 million. On Steam your game doesn't sell at all on full price but at 50% off all potential customers will buy the game. So with a 50% discount on Steam you will make $60 * 0.5 * 0.7 * 9 mil * 0.5 = $94.5 million.

You can literally have Steam take a bigger cut than Epic and sell the game for half a price and still make more money on Steam because the userbase plays a huge role in how much money you'll actually make. That is why you see all time lows on Steam, because you can sell your game for cheaper than any other store and still make more money on Steam.