Intended use matters quite a bit (Score 1)

It's difficult to advise without details of intended use, but generally I think it through like this:

• Your solution is $5K, alternative $50K.
• Do you have $50k to spend? If all you can spend is $5K then this is the right choice.
• How much time our you going to spend on-disk? Not much? Great then use those savings to buy a poopload of RAM for your memcached servers.
• Already have RAM maxed out? Oh well use some of that money on more efficient power supplies for your perlbal/pound/nginx load balancers.
• Load Balancers? Look dude, I just need to store alot of media.
• Oh! why didn't you say so, just use Amazon S3.
• What's that? You need in-house reliability and speed? Oh ok.
• Buy the $50k SAN.