It's Russia - offer $30 US, or 25 Euro and see what happens. I have always found that offering to pay helps, and if you are really that against sitting with the commoners this is a reasonable price. If I remember correctly, a cappuccino and a cake might cost you that anyway. But it is not unpleasant to sit airside, IMO. Some good views of the activity, comfy chairs, decent-ish food, etc makes it ok. And if your friend makes you sit there on your own, well I would question their "friendness".