Me: Costs nothing because I use an automatic time tracker called WakaTime [1].

However, I only track time outside of work when invoicing contracting clients.

At work I only track feature velocity not time. At work I only use the automatic time tracker for goal setting, leaderboards for fun, and to just see my stats such as time I spend waiting for code to compile vs writing code.

[1] https://wakatime.com

Through my career, it was dependent on how much transparency my boss would like to have. When the choice was mine, we didn't track due to cost and to avoid the feeling of being watched. In my last company I did this for invoicing the customers and it was few hours a month. Quite expensive since I was high up in the hierarchy.