Unit price * quantity equals what? For example if widgets have a $10 unit price, and a customer buys 3, then what is the $30 amount called? Total doesn't work since there could be other products purchased, as well as discounts or VAT calculations applied later.
In some settings, the established term for this amount is extended price or extended cost. The term is, however, unlikely to be readily understood by the general public, and it should thus be reserved for business-to-business communications in the fields in which it is an accepted part of the jargon.
The general word is subtotal:
: the sum of part of a series of figures
// Your subtotal is $14, and with tax, that will be $14.70.
Depending on context, a subtotal can represent the total of each product or the total of all products before tax and other calculations.
The site NuORDER also mentions subtotal:
This is the total price for each product in your order or the total price found for a selected delivery window in your order.
Again, note that context can change what subtotal refers to specifically.
However, they also use the term item total (in addition to both subtotal and total amount) in a screenshot of an example order summary: