It's not so much about what they maybe could get for him, it's about what trading him for less than an exciting return would do to their fanbase.
If you're the Grizz, is it worth p---ing off your loyal but small-market fan base just so you can get Marcus Smart and a decent-not-great lottery pick?
This is true. he's probably the greatest player in franchise history. With no banners to fall back on, how does Seattle Grizzlies sound?