Let’s all agree that thank you notes are not required or necessary but are a nice thing to do. There are programs that like receiving them. But they are not a requirement. You can make your own decision as to whether you want to send them or not.
Personally, I would still err on the side of sending them. We sent them to programs we were no longer interested in as well as ones we were. We sent them to everyone. We were not begging @halflokum. We were thanking them for the opportunity, to be in front of them, for their time and for their feedback (that yes we paid for). That is what we felt was the appropriate thing to do. All of you should do what you feel is appropriate for your family.
And @connections, it is true we did not send them if all we did was submit an application to a school without ever meeting anyone from there. But, if we did an on-campus tour for any school (MT or otherwise) we did also send them a thank you note. This includes applying to a “regular” college. We only sent them to people we were in front of in person. But we still sent them. It is just what we felt was appropriate to do. (and yes we paid for our applications for “regular” college too, but still felt it was appropriate to thank them for their time).
Again, to each his own. I think it should be clear to all now that thank you notes are not required. But there are people who feel it is a good thing to do. As with all things, choose what suits you best and allow others to make their choice as well.