Interesting... I have heard of schools paying for trips to an admitted students weekend (to increase yield rate) but did not realize they would try to woo you even without an application.
You can always call the school and say you would be happy to come but chances of you actually applying are pretty slim - do they still want you to come and give it a shot? That way, the ethical dilemma is out of question (and I would not be surprised if they said, yes do come even if you are not planning to apply)
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