1- the ND price you quote is for 45 min, yet the AM price is for 1 hour. The comparable AM price for 45 minutes would be (28,000*0.75) = 21,000. Nearly the same as ND.
2- ND is much more expensive in other time brackets: for 35,000 you only get 90 minutes at ND, but for that same 35,000 you get...