I remember to read an interview of one actor who told that one day, during a take with one actress, he had a hard-on. He felt so bad because that is forbiden! Obviously he wasn't a porno actor.
I think that Masha is a real nymphomaniac and needs sex everyday. Sometimes, several times, when was younger. But her sex with TK was different from Sasha. We could see in her eyes!
For Dasha and Masha, Sasha is a poor guy that helps them in the job. The penguin, sometimes is furious, when he feels he is being used by Masha.
(This is my "answer" for bean1111 comment. Thanks for commenting.