1) You take misquote me on purpose, disregarding the terminology distinctly stating: "if it was the only reason". Aka: I argue that you ignore additional content, and how it to a customer justifies the subscription model in a way servers and maintenence does not. You seem to be under the illusion that F2P titles or B2P titles doesn't have similar issues in managing their games. You still chose to ignore the idea of additional content justifying subscription models as relevant, hence you fail to address the issue I raise. Please be more constructive in future, rather than acting stubborn just for the sake of being stubborn.
2) Beep!
"You forget that even a 'stale' game would still need near-constant development: weekly maintenance, updating for new hardware and software drivers as well as new OS's and OS updates that will come in the future, as well as fixing whatever bugs those updates may cause."
I never forgot that, that is included in my reasoning as F2P MMORPG's and B2P MMORPG's address the same issue. You still refuse to accept than equal pricing for a lesser product (in terms of content updates) is unreasonable. I will not continue this discussion if you continue to grasp at straws to avoid that fact.
3) "No, it's not. That's you just building and attacking a strawman. Again, it's objectively wrong to force players who are not interested in vanilla servers to pay for others who want to play vanilla for free."
This speaks for itself. You are allowed to construct false premises based on assumptions, and I am not even allowed to raise questions regarding that by bringing up the only way your assumption could prove relevant? Failure to comply with reason? Check. You like to state something is objectively wrong when your entire premise is a subjective viewpoint on the whole debate. In which you have admitted you do not like the concept of paying for legacy servers. As if that was the actual case when finances are involved in development...
But you know what IS objectively wrong? Making up bullshit assumptions from a subjective perspective to justify ignoring valid reasonings as to why the price of 15 USD per month for legacy servers would not be fair.
4) "The only ones being "entitled" are the ones who believe that people who don't care or don't want vanilla should pay for those servers so the pro-vanilla crowd could play in those servers for free."
You a) confuse a F2P payment model with being entirely free of cost. F2P titles can in fact end up making more income per costumer than a subscription model, depending on how well it is implemented. Then you b) accuse others of being entitled for stating their desire to play on legacy servers, while you proclaim that you do not wish to pay for those costs out of your own pocket and refuse to accept that you are as a result "entitled"? Hypocrite.
5) "And you're going to argue that costs would be minimal, then?"
Nay, nor did I claim they would be so minimal as to amount to nothing. You assume I do.
"You do know the issue is not about creating one, two, three, or even ten vanilla servers, right?"
Uh, actually, the number of realms in question would indeed have something to say on the expenses. Hence, why Blizzard shut down some dying realms and merge realms. To avoid some expenses. There are of course other factors to consider.
"[...]most of it resides in re-working the code to make it fully work with today's hardware and software."
Code that exist for reference and is frankly a one-time endeavour, but would amount to quite some time. It doesn't necessary require dozens of people working on the project. In fact, as provided by the statements regarding legacy servers in the case of Runescape: far less.