Let the hive mind of Engadget get that for you.
"I'm looking for a solid state drive, around 32 to 64GB, for use in my web server. The drive will contain my web sites and the operating system, either Windows Server 2008 R2 or Ubuntu. Large storage is handled by a separate RAID array, so capacity is not an issue. Rather, I am looking for the fastest, longest-lasting, and most reliable drive under $150 that is suitable to my application. Any thoughts? Thanks!"
That's like asking why Cable and DSL charge the same for internet service regardless of whether you buy a modem or lease one or give you one for free as part of a contractual promotion (in the case of DSL).
What you use doesn't change. The only reason why you sign a 2 year contract is to get a discounted phone.