Is dealing with Google AdSense in the manner described, where the financial compensation for each ad click varies and the user is unaware of the amount of profit before clicking, considered an act of ignorance (jahalah), and should one stop using it?

If the advertiser knows the value of advertisements and their variations, there is no harm in that, because what is known by custom is like what is stipulated by condition. Scholars have indeed stated that custom is to be considered in the wage. However, if the subscriber does not know the wage corresponding to each click, then this is an ignorance that invalidates the contract.