The “good work Wesley, I’ll probably charge you in the morning” plan.
Sure, it's inherently a tech/financial/support load to maintain a special category of customer, but I don't see it as fundamentally any different from a successful company managing the discontinuation of a popular product. You cut off new customers, let attrition take its course for the existing ones, and take your lumps from any high-value/high-touch customers who drag their feet on moving to the new thing. It's work, but so is climbing a ladder. Do you want to elevate the company or not?
It’s really hard to quantify the positive benefit of letting them stay, and really easy to quantify that letting them stay is going to cost us $500/month forever.
The reasoning breaks down here. There's not likely to be a lot of attrition for a free product compared to a paid one. It costs nothing to continue and costs time to cancel.
Because their responsibility to do so hasn't (yet) been translated into legal liability.
A lot would change if someone could successfully sue a company for not keeping one of these sorts of promises.