The popularity of Amazon's EC2 cloud platform has increased in recent years. However, many high-performance computing (HPC) users consider dedicated high-performance clusters, typically found in large compute centers such as those in national laboratories, to be far superior to EC2 because of significant communication overhead of the latter. Our view is that this is quite narrow and the proper metrics for comparing high-performance clusters to EC2 is turnaround time and cost. In this paper, we compare the top-of-the-line EC2 cluster to HPC clusters at Lawrence Livermore National Laboratory (LLNL) based on turnaround time and total cost of execution. When measuring turnaround time, we include expected queue wait time on HPC clusters. Our results show that although as expected, standard HPC clusters are superior in raw performance, EC2 clusters may produce better turnaround times. To estimate cost, we developed a pricing model - relative to EC2's node-hour prices - to set node-hour prices for (currently free) LLNL clusters. We observe that the cost-effectiveness of running an application on a cluster depends on raw performance and application scalability.