The right customers -- professional developers -- would want the tool to stick around for a while, but of course there is a free-loader problem.

Paying $100 a year, let alone $100 once off, for something that improves productivity ought to be below the level of even caring to do the cost-benefit analysis.

If your employer won't let you spend $100 on a productivity tool, he's very foolish. (NB: Most employers are foolish. I've always got hemming and hawing about spending that money; can't we just do without?)