Just another perspective to consider.
As much as I agree with you Q about how you
should write thank yous, I think this your argument is not a real world argument. I will give two reasons as examples.
First, the interviewing program is getting trainees or slave labor for their programs. In the case of MD/PhD students, the medical school gets a high quality lab rat. In the case of residents, the program is getting an employee/laborer. They have a vested interest in interviewing you. Even for a md program, they are getting large amounts of tuition out of you.
Second, when I used to student host, I went
far out of my way for the people I'd host. I almost always altered my own plans, took the hostee out for drinks and/or dinner, I sometimes cooked for the people I hosted, I always had to make them a bed, wash their sheets/towel, etc... I have done student interviews, and the time and effort invested in those per student really pales compared to the time I spend on hosting.
I almost always received thank you notes for interviewing. I almost never received a thank you note for hosting. I never once received a gift. Once someone bought me a drink at the bar after I complained about this phenomenon to him. But, the people I'd host never usually even offered to help me at all. The people I'd cook for didn't do dishes. They never even took down their sheets on the bed I provded for them. One guy puked in my trash can and didn't even take that out the next day when he felt better.
So I'm a bit jaded on the whole thank you note thing. A real heartfelt handwritten thank you is one thing. I've received that exactly twice in dozens of interviews. What I usually get resembles a form letter. It looks like it could have been written to any interviewer and they just changed name of school X to my school. Once my interviewing is done I have no further feedback on the applicant, so it really doesn't matter if you write me a thank you note or not. But this formality of sending letters just irks me. If I could I would deduct points for the form letter people. Especially since they tend to be "thank you for interview me, now let me spend the rest of a full page telling you why I'm great."
Once I started giving my e-mail address out, I started getting one or two line thank you e-mails instead of form letters. I feel rather the same way about that.
So my opinion is handwrite a real, thoughtful thank you note. Or don't bother. But that's just my own emotional opinion that has no basis in reality.