The s at the end of tous is always pronounced when tous is used as a pronoun. Some examples:

• J’avais invité cinq amis, tous sont venus.
• Venez tous !
• Tous les mêmes !
• Du travail pour tous

Regarding “tous les”, in most cases this is used as the English would “all the X”. For example, “tous les invités applaudirent” means “(all (the guests)) applauded”, where parenthesis indicate levels of grouping.

On the other hand, “tous les mêmes” is different: it implies “ce sont tous les mêmes”, “they are all the same”, in which tous is actually an adjective.