I do agree that having to constantly insert values manually can be a bit burdensome (especially for splitting items since the split window has the default value of 1 which most often than not has to be modified).
Regarding the game remembering your previous entries it doesn't sound much like a good fix. Maybe allowing to type "k" when setting prices will add three zeroes automatically.
And as far as sorting and managing the inventory goes, I think they could borrow some ideas from Minecraft in terms of simplistic, yet sophisticated inputs.
But, as always, we can keep on dreaming...