It's enough, granted, to get me to buy the game, and admittedly, there will big big chunks of that list I maybe only use once/twice, or maybe even not at all.. but the more cars there are, the more that are likely to be the ones I, or any individual player will want to use. It's not hard to pick any brand, class or era that doesn't have massive gaps that people would reasonably like to see filled. As a simplified example, for me to get the 5-10 BMW's I think are serious omissions, PD will probably have to add 400 cars, for me to get "more than enough" BMW's, they'd probably have to add double that (like I say, a simplified example, but I'm sure we all have groups of cars we prefer).
... as for that being a wildly unrealistic expectation... Yup, almost definitely. I'd love to know from Kaz why that was so unrealistic though. I'm one of those that would happily pay for DLC if it allowed them to fund that kind of expansion. If they can put 400+ cars out, for £70, why doesn't ~£5 a month for a DLC pack allow them to produce 25-30 cars a month? And that's a genuine question, not an expectation.