In order to properly care for a hedgehog, you need at the very minimum:
High quality cat food, like Innova - $20/bag
Heating pad (they will die if they get too cold) - $20
At least a 20 long terrarium - $30 or so, but BIGGER IS BETTER
A wheel with a solid running surface, big enough for the adult animal - $20
Bedding - $15/bag
A commitment of 3-5 years
Hedgehogs aren't a "get it and leave it" animal. If you don't socialize them frequently, you'll quickly regret getting one. As mentioned above, they have VERY sharp teeth and of course their quills to let you know when they're not happy. They're insectivores, so they need a lot of high quality protein in their diet. Even your store bought hedgehog food isn't really adequate for them. Furthermore, they run up to 2 miles a night in the wild so they need a wheel in their cage or they risk developing numerous health problems related to obesity.
I really wouldn't recommend getting one unless you're SURE you have the time, money, and space. This is one of the more frequent animals I see up for adoption due to people impulse buying and then 3 months later realizing they got more than they bargained for.