> If this tool saves that person 90 seconds a day finding and tweaking things in...

> If this tool saves that person 90 seconds a day finding and tweaking things in a design then it's saving more than $30/month worth of their time.

As pointed out elsewhere, it's saving the business more than $30/m, not the developer.

The developer doesn't get to pocket the savings. Their reward for "saving" 4 hours a week is an extra 4 hours of work per week.