Loyality points giving you skill bonus (max .50%), 360 points giving you bonus of 5% so easy. 1 point = 1 day of premium. So easy to calculate.
Average if scroll cost 2kk~, and you need 10 years of premium activated on your account :
12x100x2kk = 240kk - Total cost to enjoy of 50% skill bonus
It won't give you mlvls, just booster to gain mlvl/skill faster = drink less potions/train less time