“full” premium removes all advertising, and it’s quite pricey in the US. “Lite” premium removes ‘most’ ads but doesn’t allow downloads at all.
It’s $16/month for full premium. It’s all relative, but I wouldn’t describe that as quite pricey for a platform with that large a library.
I believe the ads that "lite" Premium doesn't remove are on anything that has ContentID music in it, as they have to pay higher fees to the record labels for those.