You are not buying a "product". You are buying a license to use the software under some conditions one of which could be that if you use it year after year you

You are not buying a "product". You are buying a license to use the software under some conditions one of which could be that if you use it year after year you must pay more. Nobody is "forcing you" to pay for updates, they are selling you a license. And since they are the seller they can write the terms of the sale.