How long if you build it your own incl electricity prices? If margins are similar to other EC2 instances, you'd probably break-even after 6 months or so. Which makes EC2 uneconomical for any lab/company that can utilise the cluster 24/7.
Still nice if you quickly need to get some model results though.
Amazon prices are for the pay as you go model. You can shave a significant amount off the price if you know you're going to be running them for 12 months.
Still nice if you quickly need to get some model results though.