Different people have different needs.
Someone who is new to the world of DAWs and doesn't have a big collection of plug-ins and instruments sees the bundled add-ons as tremendous value. They receive drums, plug-ins, synths...you name it. Write a check, get a studio. You could easily make a case that these add-ons are worth $199 to someone.
A veteran SONAR user sees value in additions to the core program with features like VocalSync, Mix Recall, etc. etc. etc. You could easily make a case that all the core program enhancements are worth $199 (but of course, if you pay $149 now you also get enhancements and content throughout the coming year).
So Cakewalk's tactic is very simple: Provide much
more value than the cost of the upgrade so that even if someone doesn't use half of it, what they do use
still provides considerable value.
A good analogy is Native Instruments' Komplete. It probably has a lot of content, processors, and maybe even instruments that people don't use (although different people will use different parts of it). But if you were to buy only what you did use separately, it would equal or likely exceed the cost of Komplete. So you just buy Komplete, get everything, use what you want, and still come out ahead.
Don't forget that content is a part of the membership program as well. I just finished 375 MB of R&B bass loops from Public Enemy's Brian Hardgroove for the Membership program. Will everyone use them? No. Does everyone want them? No. Will some people find them extraordinarily musical and useful? Yes. Will some people who thought they would never use them end up using them? Yes. These may or may not be the same people who find my collection of pad loops (which stretch from 50 to 500 BPM without artifacts) useful.
The doomsday scenarios seem to assume Cakewalk doesn't want to stay in business. I can assure everyone that Cakewalk very much wants to stay in business, and they've decided the way to do that is to provide so much cool stuff over the course of a year that people will want to renew for another year.
As I've said before, the burden is not on users to renew. It's on Cakewalk to provide something that
causes people to renew.