Product Price List selector

I’m trying to understand, the need of d632eee3c4c3e1423f858e86d98fa34efffda20a.

Why we need a selector for price? Don’t we have unit_price, list_price and cost_price that should be enough?
Shouldn’t we add a migration to UPDATE product_price_list set price = 'list_price'; to keep the same usage as previous versions?

Otherwise unit_price is not defined.

we did this on migration to 7.0, too.

Unit price was always list price, wasn’t it?

But now we have a third option (the default one) which is none and now is not defined.

So why we need such option if there is already a variable for cost_price?