Before the advent of the computer financial handbooks contained tables which showed the values used to calculate the cost of annuities for various time periods and discount rates. These days an Excel spreadsheet can perform this task. Example 2 at the below URL shows how.
A 20 year (240 month) monthly annuity discounted at 1% per annum has a present value of $217,441.27 per $1,000 (and $869,765.06 for 240 monthly payments of $4,000).
A 30 year $1,000 monthly annuity, discounted at 1%, has a PV of $310,907.07.