Marginal Revenue

The difference in revenue earned by increasing production.

I make 100,000 pens earning a profit of $200,000. A customer wants to buy 10,000 additional pens. If I accept that order I will earn $220,000. The marginal revenue is $20,000, the difference between $220,000 and $200,000. It is the extra money I will earn by making 10,000 more pens.

https://accounting.uworld.com/cpa-review/lc/accounting-dictionary/term/marginal-revenue/