This value is highly subjective. Of course you can spend more money on a night out with friends or less with a very good single player game. This is not for you to decide and judge (if it is of value enough for you, fine. Still you waited for a good sale as well and did not pay it monthly for a higher rate). I already explained in other threads last year, why a longer subscription has drawbacks...just ask those who resubbed for 12 months early before this incoming change.
These changes so far represent a true value/money reduction, so far from petty. And the last thing funcom needs now are annoyed customers or a lawsuit (even if they win it! on the other hand it can be seen as "change of contract" and might be valid for an immediate subscription cancelling with money compensation). I am not saying that they can not change membership models or that it would be a bad idea, but you can not nerf it (or deliberately turn it into a lottery and put customers under pressure for rewards) without giving in return. You need to have a working plan for the transition and when in doubt better go in customers favour, especially if you are in funcoms situation. You can not experiment, if you are responsible.
They said themselves that they will reduce the new subscription price (at least for first month), which is good, but still requires some kind of objective compensation, unless you want to risk loosing customers over this (e.g. real money...and last time i checked funcom needed money, right?). And these are not "potential" customers like f2p, this meddles with the core of the companys income (a subscription model that sustained and paid their bills (yours too?) for years).