I’m on the side of not sending a note, regardless of how generous the gift may be. If I thank you in person I have thanked you.
When I first started to read this, I thought it would be about something else. I was mainly fooled by the title of the question. See, to me thank you notes are highly undersirable.
This is a loose notion I have in my mind, a part of my nature, so finding words may be a little hard to do. lets see…
I can’t immagine a true good friend ever giving another good friend a thank you note. they would not even say thank you, they would probably only say “thanks”. If someone sent me a thank you note, all I would see is “we are not really friends, so lets keep this formal”
A thank you note is something you send to a stranger, like a paramedic who saved your life. it is not something real good friends do with one another.
Also, if you expect a thank you note for a gift, then you are certainly not going to get one. as its not a gift at all, because you expected something in return, namely the note.
To me, thank you notes say “im pretencious and superficial, I’m formal, and I will never help you when you really need it because we are not really friends. I only gave you the gift because of my social status and I was only realy trying to buy you. the gift was not for you, the gift was just a tool to facilitate my own gift of having everyone in the room tell me what a cool guy I am.”
As for not attending because of the lack of a note, that just screams out all kinds of things. that mainly makes me suspect the relative is not a nice person at all, and would prompt me to send the gift back, along with an additional gift of my own, and an envelope full of money, and a note telling them to stay out of my life.
I’m probably not explaining my self too well here at all, and probably making my self sound like a maniac, but there is method in my madness. ... i think
If you give me a gift, its just a material thing, so I wont really appreciate it that much. I will probably like it, and maybe appreciate it a little. But im more inclined to appreciate non material goods more. such as loyalty and trust. If i do appreciate something you do for me, be it material or not, I will thank you in person, but I will never send out a note. If i appreciate something you did for me, you wont get a note, but it will show in other ways, you will have my loyalty, and if anyone ever tries to harm you, they would have to go through me first, i would be there when you need to move home, and i would be there when you need money, but you wont get a note.
Finally, gifts are standard social practice at weddings, if you have just got married, i expect you to go on yout honeymoon and not even think about me. i would not even expect you to remember I exist, much less send me and everyone else who gave you a gift a silly note. Go and get on with your honeymoon and have fun, its all about the happy couple, and not about me.