"I quickly put together a small app where I could input the prices and it would output monthly/yearly cost, cost for free users, paid users, etc. so I'd be able to process the information immediately."
Assuming his goal was to be ready with results of his calculations in real time while on a call, which may happen while you’re away from your computer, it makes sense I think. Excel is great, but on phone while away from your computer? Not so sure.
