because it is reasonable to expect prices to go down over time.
Membership

According to the membership page, the only differences between Platinum and Diamond are Chess Mentor time and access to computer analysis.
There are some more substantial changes that you've mentioned between Gold and Platinum levels, but there it's showing me a difference of only $1.50 a month, and if the main reason is using more than 25 tactics a day it still seems pretty cheap to me.
If you did just 50 per day, then you're doing roughly 5 tactics for every penny you spent to upgrade.
Personally, I'm not going to make great use of a lot of benefits that I get, however I use enough Chess Mentor time when I get the urge to do some of Silman's positional analysis every month to make this a pretty fair savings to my yearly budget.
Perhaps the incentive isn't so much to upgrade to save money, but to upgrade(cheaply, in my eyes) and then try the new features you get to go with the ones you want anyway.

Not really. Most prices go up. Thats what I would expect. I would also expect to get more for my money though.

You expect to get more for your money? No offense but your economic understanding is as limited as the real Joe the plumber.

for me its ok.
and, for any changes, there are pros and cons.. but of course most of them are subjective.

Um, im assuming you buy a computer once in a while.
Well, im also assuming you paid less for the most recent one than you did five years ago but im also assummng that they put a bigger HDD, more ram, better processor etc in the box If not, you got rpped off. Also, i bet you ahe bought some gas in the last couple of weeks. Did you pay as much as in August, probably not. Also, its hard to tell if you got diamond for life or not anymore, but, if you recently bouht that diamond membership, i bet you got more for less money than last week.
My point is that the value of many things change, and it just seems to me that the value difference, realitive to the price difference of the memberships is small. Im simply suggesting to Chess.com that they just gave use great new features, but that created a negative incentive to upgraade from gold to platinum.
Im staying with gold, at least for a while. I might try a month of diamond but it seems almost useless since I can see what I get on the membership page and its not much more of anything I use.

Basically, what ive been saying all along, is:
I was expecting that, in order to encourage the subscription to platinum and diamond, there would be better incentives relitive to gold; but as of today, Chess.com gives away a lot more to us Gold members but not much more to you platinum.
Eric, give me some extra real good stuff in diamond and ill upgrade today.

joetheplumber> I was expecting that, in order to encourage the subscription to platinum and diamond, there would be better incentives relitive to gold.
Hmm... Diamond memberships now include Chess Mentor and can be purchased on a monthly or yearly basis, and Platinum memberships are slashed by 40%, so there's more reason to upgrade now than there ever was before.
I have a few comments to make and they are all about memberships.
Firstly, thanks for all of the work that went into today's chess.com upgrade.
I know this upgrade was to avoid confusion, but to me it seems a bit worse. Now instead of two membership levels plus Free, we have three plus Free. The monthly non monthly seems to be solved, and the prices seem reasonable for all. The elimination of Mentor subs also seems to make things easier (although ive never found myself particularly attracted to the Ches Mentor.) It seems that if I renew as a gold, that Ill actually be losing benefits, such as TT and not really gaining anything, except maybe that computer thing. Im encouraged to do platinum but thats 50 bucks a year. Not much, but a fair bit more than 30, and for what? Tactics and Computer analysis of my games? And mobile, which, because of its format will not work on my phone.
I guess what im trying to say is that although these memberships are a very reasonable value, there's not really an incentive to upgrade. I was looking forward to the better price scheme and maybe some great new benefits but it seems that they basically upgraded the entire site so that I can keep my gold with no worries.
I like the changes, for the most part, but im not sure that the business model is so strong. Next time upgrade platinum and diamond and take more of my money away.