It was probably a typo, but that isn’t correct. If you buy four $250’s you get $1,000 CNC and pay $500.
The best way to deal with this is to ignore all the promo stuff that NCL use, don’t talk to the cruise next staff about it and just remember this:
1 CruiseNext (worth $250) costs $150
2 CruiseNext (worth $500) costs $250
3 CruiseNext (worth $750) costs $375
each additional $250 CruiseNext after that costs an additional $125
Thats it. Forget talk of OBC and money to spend. It is a simple discount, nothing more than that.