They may not sell you a lift pass unless you book a hotel through them which is why it probably works out cheaper to go on a package tour. You can but try !!
I have heard Lift passes will be about 50 leva a day this year, very bad news for those of us who live here and have residency. As the two tier system has been scrapped. Resorts will not be able to have a two tier system of charging as this is now the law in Bulgaria