Thanks for doing the maths on this. Going through my SDB is just so slow and tedious that I likely won't donate enough to get both the stamp and the background. Now I can see that I should use my points on the background and buy the stamp for NPs!
Probably the only good thing to come of lowering the prize points is that I can now easily buy the prizes myself as their value will decrease. Now lazy me doesn't have to go through the painful process of donating. I got through about 10 pages in my SDB before I got bored/couldn't be bothered anymore.
This was going to be my first year participating in Charity Corner and I'd built up so much excitement after months of hearing about all the prize perks I could get. Now I'm bitterly disappointed that the entire event has been changed up. Been hoarding away Sticky Snowballs for nothing and the prize pool isn't even worth participating for.