Sale price : "Base price to compute the Customer Price"

Cost price : "Base price used on purchase order"

Base price simply means minimum value price, it can be vary according to the customer(Sale price), supplier(Cost price), or price lists.

Sale price is the default base price occurring in sale order

Cost price is the default base price occurring in purchase order

That what i'm saying. Let an example: customer A & customer B. We set a sale price for product as 100.

We sell the customerA with product as 100 which is the base price of the product

We defined a price list for customerB

New Price = Base Price * ( 1 + 0.0000 ) + 0.00

here the Base price value comes from the sale price field. So the new price New Price = 100 * ( 1 + 0.5000 ) + 0.00 = 150

So customerB sale price for the product is 150

But the default base price or sale price is 100 for all customer.