Depends on your investing strategy. If you’re a buy-and-hold, it makes way more sense to buy as many shares as possible, which means buying at the lowest price possible.

I’d argue it IS better to buy at 40, or even to miss the bottom by a few bucks and buy at 45, simply because you will get MORE shares for your investment at 40–45 than you will buying blocks at 70, 60, 50 etc on the way down.