My only interest in Monte Carlo is to wear evening dress and go to the Casino, maybe Café de Paris. If I spent a night there it would be to enjoy a beautiful hotel, pool and beach but I might get a similar experience in another town at a nice hotel for less.
Since it is so close, why not?
I don't find it much fun to window shop for things that are unaffordable. I prefer little local boutiques. Markets can be ok too.

From what I'm seeing, Sanremo is a bit down at the heel despite some nice (and relatively inexpensive) beachfront hotels.

Sanremo is a bit, but nice gardens near by

My only interest in Monte Carlo is to wear evening dress and go to the Casino, maybe Café de Paris. If I spent a night there it would be to enjoy a beautiful hotel, pool and beach but I might get a similar experience in another town at a nice hotel for less.>

But that type of experience it seems can only be done in Monte Carlo where the Casino is well grandeur but yes it comes with a cost. Go for it - about the only reason to stay in Monte Carlo.