I take back what I said earlier. The affection scaling is bloody awful!

At the moment I am leveling a recently obtained girl to max affection. In total, she requires 8,385 affection (She is my 39th girl in total).
Currently, I am sitting at 3,319 affection. She requires 5,066 more affection to be able to level her up.
To get there, I am going to use Bracelets which produce 60 affection per Bracelet. I'll need to use 85 of these to fill the remainder of her meter.
These Bracelets cost $25,021 in the shop, or have a chance to drop from the pachinko. The latter being the best option if you're looking for affection material.
85 multiplied by 25,021 comes out to 2,126,785.

That's right. I am spending over two million dollars just to fill her meter. Keep in mind, I am not even factoring in the amount I've already spent, nor am I applying the additional fee to upgrade her.

I don't even have words.