A keyboard is a tool. Would you spend extra money on quality tools? I would and I do. Get a nice jack, a nice wrench set, a nice keyboard, a nice chair, a nice monitor.
The keyboard shown in this video is not something that I think is worth $240. It is a gimmick.
With that said, I have spent about $50 and $60 for my two keyboards, respectively. A rubber dome one for work, and a mechanical for home. I type faster and more precisely on it. My hands feel better on it. I use the two all day, almost every day, pretty much from the time I wake to the time I go to sleep. Of fucking course I will spend a few bucks to get the right tool for the job.
Oh, and from an ROI standpoint? If a good monitor and a good keyboard let a programmer or an engineer be only 1% more efficient, considering their total cost during their time at a company and the revenue their work generates, the purchase will pay for itself in a very short time. Practically speaking, a good monitor setup (usually something like 2x 24" professional monitors), good keyboard and mouse, and good chair, will increase productivity so much that they will pay for themselves inside of a single pay period.