Yea, you pretty much hit the nail on the head.
The original number pushed ($9B) was a pure purchase price, and the "big shock" $25B is a 20 life cycle cost (including fuel!) that the MPs already knew about but someone decided to jump up and down about. Yes, the public really does appear to be that uneducated :(
I have very mixed feelings about the F35 program. On one hand, it was/is a sole-source contract. Normally for a big capital project like this companies need to bid their wares, tests are done, reviews are held, and the best 'value for money' is purchased (see Close Combat Vehicle CCV, and Tactical Armoured Patrol Vehicle TAPV procurements that are also ongoing).
The F35 is different because when the project first started up 20 years ago, Canada commited money to the program. We didn't commit to buy any planes, but we through in a bunch of money so we could get first hand information on the project and, ideally, have some of the construction occur in Canada. If we pull out now, we lose the potential manufacturing jobs that come with us buying the plane (if we don't buy it, the US politicians will have those duties moved to US factories). But with whole financial melt-down, it looks like a lot of the Canadian jobs may end up in the US anyways (The US wants to buy 2400 planes, we want to buy 60, you guess who gets sucked up to).
In addition to the hoo-ha of international politics and jobs, there is the requirements issue. When we purchased the CF-18 it won out against the F-16 because it was dual engine. The premise was that for arctic patrols having a single engine simply wasn't safe enough. If a pilot had an engine failure, s/he could be too far out, in too dangerous conditions, to be rescued in time.
The F-35 has only one engine.
What it does have is fancy stealth capabilities. But with only 60 fighters, we aren't really going to be engaging in standing air battles with other high tech countries. The only times I see us using our air force is in situations like Lybia where we already hold air supperiority. I'm not saying stealth isn't handy (ground launched missiles are a risk), I'm just wondering how often it will actually be of use. And there are all sorts of very effective non-stealth aircraft out there that would meet our other needs (Super Hornets come to mind) for far less money.
The TL;DR version: Politicians are using these numbers to jump and yell and attack the party in power when a) the cost isn't a surprise, and b) they would probably do the same thing for a whole host of national and international political reasons. Skipping the politics of it, Canada buying the F-35 may be like Joe Blow contactor buying a big V8 super-cab pickup to transport his tools when a Ford Ranger would probably do just as well.