It doesn't matter if you can serve 10,000 requests per second if the cost of that request exceeds what you're paid for it.
For most sites ruby is profitable, the value add from ruby is decreased cycle time between releases which can increase the profitability of your site more than increasing the pages per second can.
The vast majority of sites don't need to scale beyond a single server, and when you do need to scale I prefer things like drop in support for S3, drop in support for memcached and a whole host of other performance increasing techniques over raw pages per second.
The benchmark benchmarks the very simple case of a single PHP page, what real PHP app have you used that is a single PHP page? The request times for something like WordPress are insane because of the number of PHP files that need to be interpreted per request.
edit: To clarify the jist is that low margin activities where increasing the speed of your page by 5X would have a great impact on your profitability are not the areas where you should focus you efforts. Instead focus on high margin areas where you could write your pages in SnailScript and you'd still be profitable.