How much is $100 per month forever at 12% per year worth today?

[math_celebrity]

This is a perpetuity with payments assumed at the end of each month.

12% per year = 12/12 = 1% per month

The present value of a perpetuity with payments at the end of the month is:
Payment/I

Plugging in our values, we get:
100/0.01
10,000