The problem with this statement is that you will never find two people who agree on what a "finished game" looks like. Everyone has their own priorities. Some hold RCT3 as a standard of what a "finished game" looks like, even though the community continued to add to it (even after expansion packs) because it didn't have what they were looking for.
When I first played the release version of PC, I felt that it was a finished game, as far as being ready for release. I had a lot of fun with it. That was before 3 free seasonal updates, several in-between patches, 3 paid (and optional) mini-DLC packs, and an upcoming free anniversary update (and more in the future). I don't think PC is ever a "finished game" since it will continue to grow and develop via Frontier and the community. I've certainly gotten my moneys-worth out of the original game. I did my homework and watched all of the videos and knew what I was buying. I was buying what existed at the time for the price at the time. Even if Frontier had not come out with another DLC (free or paid), it wouldn't matter. I paid my money for what I got. I expect that if I want even more, I can pay more later. I certainly wasn't expecting quarterly free updates, but got them anyway. I wasn't expecting the licensed DLCs, but they looked fun so I gladly purchased them. I wasn't expecting the spooky pack (nor did not having it prevent me from having a great time in PC). I can choose to buy it or not buy it.
This update doesn't "complete" PC for me. No update will do that for anyone because it won't address everything that you may feel made PC unfinished at launch. I respect your opinion, as much as I respect the opinion of anyone I don't know and am not personally invested in. You have your opinions and I have mine. That's ok. Find me two people who agree on everything, and I'll find you two liars.
With 'finished' I mean a game that's ready for release, aka the 'release-version'. This game at the time of those 70-dollar-alpha-access-propositions was clearly stated to be an alpha, not necessarily close to the "final" product iirc.
Whatever the community creates is something I don't include in that definition, and patches are a bit of a grey area on this, as those are (usually) intended by the developer.
Point is that buying the early bird was completely optional. No one was forced to spend the money. There was an option to buy the regular game at a lower pre-order price than what it was after release. Frontier never said that you would get a complete, or close to complete, game during the alpha/beta period. They laid out the road-map ahead of time, telling us it would be three phases plus a short final Beta test that also invited people outside of the early birds program to participate in. The whole point with the early bird program was to get the core players, that were willing to pay the $70 it cost, to test the different game mechanics on a larger scale and give feedback to Frontier. That happened and made it to the game we have today. A lot of core items in the game today were influenced by the early bird players. Another way of looking at the high price is to weed out and limit the player base during this phase. Having too many testers would not be good either and you could, hypothetically, get feedback reports from players that didn't really care about the game. Enough of these reports and the game may have taken a less fortunate route. This is just speculations, but the price tag did in fact limit the number of alpha/beta testers which I think was one of Frontiers goal.
For people to complain that they did not get a full featured game during the alpha/beta process makes no sense. You only paid to get early access to the game and a chance to influence it. If you didn't believe Frontier would deliver a product you would like, maybe you places your early bird bet on the wrong horse.
In order to buy something, anything, most people first do some research if they don't know enough about the product they are buying. Some products you know by experience, like milk or eggs, if they are good and worth your money. Some need research, like a car. If you can't find the information you need in order to make the purchase decision, well then you have two options, you either don't buy the product and wait until you have gathered the information you feel you need, or you take a chance/risk and go ahead and buying it, knowing it may or may not turn out the way YOU hoped for. There is also a chance that it would turn out even better than what you could have imagined (that is my feeling about the game but certainly not everyone's since we all have different bars that sets the standards for ourselves). Basic risk analysis.
Even if it were completely optional, that doesn't make it automatically good business practice. For an example, the "From Ashes"-DLC for Mass Effect 3 was completely optional, but it is still a dirty move to lock important story points behind a first-day DLC-pack.
It's nice that they communicated clearly about what the game was going through, and steps in development. But it still doesn't change that those buying the game at that time basically paid for play-testing, which is something developers normally have to pay people for as a job. If following that train of thought, and lack of direct knowledge of that stadium, I hope you understand why I'm a bit sceptical of Frontier?
Yes, people should research what they buy. But not everyone has enough time to properly assess it without faling into biases, especially if they're excited/hyped about it. If you throw on that possible lack of proper info and criticism (Like "Shadow of Mordor" not allowing reviews iirc) and nasty PR (like the entire fuzz about Dishonored 2 and pre-orders, foe example), and it can be rather hard.
Add to that that a fair amount of possible buyers are fairly young or blindly defend a company/IP, and thus not quite that good at applying critical thinking to such a product, and you get a lot of people taken advantage from.
I just really hope the pack is worth the price, so I can buy it with certitude. Otherwise I'll wait until a price drop, or it is combined with other DLC's as a more sizable pack with a better value proposition.
Now that the Scope of Darkrides is getting expanded... Boat Rides are next right? 
