The Crystalline core compendium currently on PTS 2nd Dec costs 400 crystalline cores.
They can fill and proc one time a week, that gives you 5 whole cores.

So to make it and then get it to pay for itself long term will take 80 WEEKS.
or in other words over 1 and a half years of playing and filling it to make any extra cores over the cost of the tome.

Please Either reduce the cost of resources or the quantity of the reward it gives only 1 time a week to a level where it will only cost like 10 weeks to recoup the initial cost.

Otherwise It would never be crafted.