Dell (among others) asks a lot more for some components than other sources do. Some of this is because they actually do extra testing and will guarantee that their components work fine in their machines. A large part seems to be extra profit for Dell though.
This is why I always buy Dell servers with minimal memory and the smallest drive you can get. When the server arrives test it, set aside the official Dell drives and replace them with your own. This way you get the best price/performance.
Do your research though. E.g. just swapping Dell branded 160GB SATA drives with 2TB SATA drives might work, until one fails and you discover it has the wrong TLER or that its firmware is not fully compatible with a HW RAID card. I spent days peering at specifications and I never had any problems with my cheap solution. Having said that. I spent a lot of time checking specifications and compatibility. If time is money for you, and it is just one server then buying directly from Dell might be best.