First, bourbon is what scotch wants to be when it grows up.
(Just kidding. Don't flame me yet.)
Andy is right. There is no need to spend $100 on liquor, although you certainly can do so. There are many excellent bourbons (depending on where you live, of course) for less than $20 for a fifth.
BTW, bourbon is a whiskey distilled from mash made of at least 51% corn which has been aged in new, charred oak barrels. There are more rules for what can and cannot be called bourbon which I cannot recall at this moment.