You're starting with the prior that buying stuff is bad and should be discouraged in general. This is quite arguable.
Nope. Otherwise people should absolutely love my approach of forcing them to buy at gunpoint - perfect conversion rate!
Even if you assume that the data implies customers prefer the fee at the end, you'd also have to research why they do so - and solve the mystery of why your statistic suggests they prefer the fee at the end, yet direct user feedback suggests the opposite.
>It is just as irrational to not buy the product as to buy it in either scenario, since the price is the same.
That kind of rationality requires perfect information. But it is likely that the price appears lower in the fee-at-end-case, because that is the only effect that the change has - so perfect information is not given. As the price is in fact the same as you say, that would make fee-at-end the case with irrational behavior.
>You're starting with the prior that buying stuff is bad and should be discouraged in general. This is quite arguable.
No, my premise is that buying stuff while you don't know the price is bad, which I think is a commonly accepted sentiment.
They presented a meaningless price when in situations where potential customers would compare them with competitors. Only when they can be sure that a customer would likely not check the price anymore (because they think they already know it or because of psychological reasons), they show the actual amount.
That's a very clear case of improving their own situation (better conversion rates) by worsening their customers' situation (higher likelihood of overspending, reduced ability to compare prices) and making them act against their own interests. This would be manipulation by the all of article's criteria.
Of course as a company you can decide do use that strategy - it's not your job to think for your your customers. But don't be surprised if consumer advocacy groups flag you and at some point you find people demanding a law against that practice.
More generally, I'd draw the line to "marketing" if you supply information to the customer that's either meaningless or misleads the customer, but could not possibly help them reach their own goals. (As in this case presenting an amount in the search results that has no practical relevance.)
I'd draw the line to "manipulation" even earlier, if you make a person act in a way that's against their own conscious interests in the moment. As I said, there can be rare cases in which that manipulation could even be wanted by the person, but I don't see that changing the fact that it's manipulation. It's different from "persuasion" where you make the person change their interests.