I meant 10% over 680... ~2x for Titan over GTX580. Where can you buy GTX580s for 200? newegg.com still has them for $400...
1k is really nothing... Consider the simple mathematics of a PhD student costing $10 / hr. Suppose you run your GPUs 24 hrs a dy for 300 days in a year (good estimate), that is 4.8k hours, if you can cut your simulation time by 1/2, that is 2.4k hours and assuming your time is worth $10 / hr, thats still 24k.
Previously we were running 20k 4x4 CPU machines, even the GTX580s were giving much more performance per dollar.
Result? We're getting something like 30 Titans... as soon as our supply channel has them in stock