are you buying one of those treadmills that you have to make run yourself ala fred flinstone? :grin: I'd go kettle ball and bike that should be under $400.
I agree, you can probably find an okay bike, bike trainer and a kettlebell all for under 400 on craigslist. But if 200$ is really the budget there's not much flexibility.
I got a good treadmill for $200 off craigslist. I also have a bike for under $200 brand new on clearance. Just have to keep an eye out.