Looking for a cheap but effective hide? I've actually found that my snakes all seem comfortable in those rotisserie chicken takeout containers. You know the ones you buy the whole chickens in? I don't know about everywhere, but where I live every grocery store has them. Many other takeout containers work well too.
Anyway, I get a tasty meal or two, then I wash the bottom of the container really well and cut out an entry hole. They are black and very low to the ground, so they provide great security for the snakes.
Unfortunately, once the snakes hit about 700-800 grams they don't fit so well. But they work for a while and come free with your meal.