I'm pretty sure what DatNexusGuy posts is correct;I feel like I've seen it here somewhere but cannot find the link...
If I find it, I'll let you know, but I do believe there is a Crystal Cap implemented. The best guess I can make for this is so that people don't get too OP from the very beginning, but are rewarded with being able to purchase more things the higher lvl that you attain. Hope this helps, and I'll post the link here if I can find it. o.o