What is the must cheapeast way to train at nmz as a pure ? Absorption+cake or using prayer pot ?

prayer pot/food to get points for absorbtion and then absorbtion

absorbtion is way cheaper

I'm currently doing it now on my pure using full robes/prayer boosting gear getting 78-82k xp/h with overloads and prayer pots. It's expensive to do because of the initial cost but over time with the herb boxes you get back you breakeven/make a little profit. It's a lot more afk than flicking rapid heal every 30 seconds to ensure you stay at 1hp as well as the fact the NPC's on hard will hit a lot more on the absorbtion potions since you're 1 defence.

Yea prayer first to get abs.
Then abs all the way