With Eve gone, only sub based MMOs left are FFXIV and WoW

[Zojha]

For me buying an expansion equals to paying for all content, while sub allows you to access the servers, hence why sub is time based and no content based, while the expansion is content based and not time based.

Well...I would advise against drawing conclusion based on the pricing model. Consider - character slots and retainers are time based (monthly) costs as well, yet once you have created the characters/stored the items on the retainers, they have to be stored all the time regardless of whether you have access to them or not (as you might want them back at some point), so they take up just as many resources. This is a clear disconnect between the pricing model and the actual resource usage. Therefore, the same might apply to expansions and the patches. Might - or might not. It's not very clear cut either way.

[alimdia]

snip

The cost of storage is almost negligible in 2016, they went down a great deal compared to the early times of MMOs, most of the resources used by players are used when they are online and active, as it contributes to server load.

But you're right that we can't know for sure how SE is distributing their income, it just for me doesn't make any logical sense to say that there's no relation between the cost of expansion and following patches, if you pay for sub but not for expansion you're not going to access heavensward content, if you pay for expansion but not sub that doesn't halt new content patches, but you can't access your character.