If your work involves using a keyboard more than a few hours a day, getting an ergonomic keyboard is going to pay back those 300 big time in the long term. Wrist and finger pain are no fun.

Though, I'd rather go for one of the pre-manufactured keyboards that had a decent amount of group studies into the design. All those boutique keyboards and designs used by less than 100 people may be fantastic or may destroy your hands, who knows? The problem is, you only find out after using a keyboard for a longer time. (A lot of folks on /r/ErgoMechBoards switch designs every few months, so the anecdata there is not great.)

Designs like the Natural Keyboard or the Kinesis Contoured/Advantage have been around long enough to know what their long-term effects are.

There are plenty of people in the 2nd hand market parting ways with their dream of ergo and mech