This cage is is based on the "grotto" style rat cage. It coast me about $150 excluding food supplies. I'm a busy collage student living in a two bedroom condo with my mother who isn't exactly a rat enthusiast. So to keep the cage clutter and coast down I made my own three story rat book shelf. I bought a press board book shelf for $70 assembled it and spar varnished it to make it urine proof. Then a carpenter friend of mine made me three separate doors to attach. I used a sewing machine and a grommet puncher to make three different types of rat hammocks installed them by using spare wood with hooks attached to the top of each unit. This cage is slightly cramped but very useful, it takes me all of ten minutes to clean on a daily basis. Let me know if you have any questions.