Well, I never paid for a DDI subscription during D&D4, and it was practically required.
I'm confused. Did you run 4e games extensively without a DDI subscription? If so, it obviously wasn't much of a requirement if you got by without it. If not, why do you feel confident enough in your experience with 4e to know whether you need a subscription to play?
Speaking as someone who has run a tremendous number of 4e games over the last five years, with and without access to DDI, a subscription is in no way required. It just makes the whole exercise easier on me, the DM. And, as a player, the Character Builder makes managing my PC much, much easier.
So I'll ask: what makes a subscription a requirement? What fundamental difference does the 4e system have from earlier systems that necessitates the subscription?
D&D5 doesn't look like it is going to have the same geometric complexity,
What geometric complexity? Geometric complexity is leveling spellcasters in 3.5. 4e is almost entirely linear in its growth of complexity. In fact, at some points, it actually
slows in growth of complexity, replacing powers instead of adding them, and selecting groups of powers/abilities in large groups rather than piecemeal (paragon paths and epic destinies).
Frankly, I wouldn't pay for a subscription to D&D on principle.
Perhaps your principles are in need of reexamination. I can't think of very many defensible principles that would require one to not pay for a service.
I buy the books -- that is my "price of admission."
No, it isn't. That's the price of the books. You got the books. You can run D&D. If you want the rest - the
convenience features that the subscription provides you with - you need to pay for them. And that's
only fair. They spent significant resources developing their software suite (a huge deal for a company division that, until now, had not really dealt with consumer software development in an in-house capacity), that suite costs money to update and maintain, and having it makes both running and playing the game significantly easier. Why
shouldn't you pay for it?
This is plainly the same sense of gamer entitlement that we've seen emerging for the past few years rearing its head.
Even the original full-price DDI plan, with the virtual tabletop, was a colossal ripoff when compared to other online services.
Nonsense. A Fantasy Grounds license that lets your players participate runs you $150. A Hero Lab license with full Pathfinder support will cost you north of $200!