I think it rapidly turns into "How much effort are you willing to use to make yourself more secure?" There's diminishing returns as you increase your money and effort devoted. $50 and a couple hours will get you another hard drive and a Linux install. How much are you going to spend to guarantee that your BIOS and firmware aren't compromised?

There's a reason why security-conscious folks spend an enormous amount of money on the stuff that we buy for a couple hundred bucks. I'm sure that the NSA pays thousands for $100 hard drives.