A lease payment is composed of an interest portion (borrowed money) and depreciation amount (purchase - residual).
The Monthly payment is then Monthly Interest Cost + Monthly Depreciation Cost
The Money Factor is used to estimate the amount of interest due in a single month of a lease so you can figure out the monthly payment.
If you are borrowing $100,000 then over the entire loan of repayment from a balance of $100,000 to a balance of $0, the average amount you owed was $50,000 (1/2 of principal).
You are repaying this loan monthly (1/12 of a year) and percents are expressed as decimals (1/100).
6 * 1/2 (for principal) * 1/12 (for monthly) * 1/100 (to convert percentage from 6% to .06) = 6 * 1/2400.
2400 is the product of 3 consecutive conversion (1/2 * 1/12 * 1/100) to convert from an interest rate to a money factor.
6/2400 = Money factor of 0.0025 which can be multiplied against the total amount being borrowed to know what the monthly interest would roughly equal.
Some Money Factor info: https://www.alphaleasing.com/resources/articles/MoneyFactor.asp