Please answer poll regarding Thank you note

DH helped neighbors with some work around their house. At the end of the day they said thank you and DH said you're welcome, anytime.
Yesterday the neighbor dropped off a gift (ugly vase) for us as a thank you for all of DH's work. I feel she should have given him something more useful but whatever.
I was going to send a thank you but DH believes it's going to start a chain reaction - they thank us, we thank them, etc.

What do you say?

i voted yes, but let me follow up. Maybe a 'note' doesnt have to be a thank you note.

How about sending them a little card that says something like 'we used the beautiful vase the other day - and thought of you' or the vase looks beautiful in our home.

THat kind of a thing?

I wouldn't send a note - they are your neighbors right? So maybe in passing next time just say oh, thanks for the lovely vase!
Very thoughtful of you.
the end.