Yes, most models converge in the case of frequent updates by the developer and regular usage by the customer and the customer upgrading regularly. The difference is, that when there are no regular updates, why should a developer get constantly paid? And sometimes, there are huge updates, which are not really reflected in value by a reasonable subscription. On the other side, the subscription model holds the customer hostage, the customer cannot decide to use an older version a bit longer and update later.
