PSQQQ supports products variants and there are two ways exist how to update variant in case if variant missed.
so we will talk here about price update.
1. do not update this variant.
it means that it at source feed there is no related veriant or if variant exists but quantity is zero than we ignore this variant at the main feed.
2. update variant with the price that will be taken from any variant for this product where quantity is more than zero (but the first from ordering by price).