I don't think CK's scores are inflated... mine certainly aren't because they have been consistently 30-50 points lower than my FICO score. I just think the CK score is not very accurate.
The CK score is very accurate. It's just NOT A FICO score. It's either, if you have the old set up, TU's "New Account" score, or if you have the new set up, the Vantage 3.0. Those are both real scores, used by actual lenders for credit decision making. The vantage 3 is used by a lot of lenders, I don't think anyone really uses TU's new account score.
The thing is that sophisticated lenders (and that's most of them these days) use multiple scores, and all sorts of proprietary systems to make their decisions. Even if they used only scores you could get, you wouldn't know how they weight each one, and which they use for binary (approved/not approved) decisions, and which they use for terms decisions. But they don't use only scores you can get, they use proprietary systems, and put different weights on things like absolute income, debt-to-income ratios, home ownership vs. not home ownership, and so on.
You can't know what they're going to do, so paying money for a useless number is a waste of money. Understand what makes you a good credit risk, and engage in that behavior.