[regularfry]

It's more a convenience tax. The nano also has battery management onboard, which is one less thing to think about. But really at that price difference picking the nano over the bare pro micro has to save me less than an hour of design time and it's already paid for itself if I'm just building a keyboard for myself. If I was looking to manufacture something at any more than "it's just for me" scale it would be a different story but it's extremely well targeted at its niche.

[jsheard]

Pretty much every nRF dev board has battery management built-in, including the $3 AliExpress ones. The chip is meant for ultra-low-power applications so including battery management is a no brainer.