Looking for a mathematician to find price points

Currently we have single item prices for products in groups of the following

1 product - $16.00
2-5 products - $14.40 each
6-11 products - $13,00 each
12 - 23 products - $11.00 each

But this is not working as some price points overlap and become cheaper per product at a higher qty.

Im looking to find someone who can work out product pricing in this way.

See the attachment and come for a chat so i can try to explain what i mean.

thanks