The Sidewinder X4 is a good keyboard at that budget, but in general, you wont find good keyboards for less than $50. That kind of budget is saturated with abysmal to medicore office equipment, not much good can be found there. http://www.newegg.com/Product/Product.aspx?Item=N82E16823109191
Follow the link, its a $50 keyboard with red backlighting that has a decent reputation for gaming. For $50 you dont even have to worry about mechanical switches, the cheapest mechanicals are at least $80.