How do you plan on making your service's pricing competitive? Amazon's current spot market instances are ~30 cents per hour, which is twenty times cheaper.
For a faster GPU, that allows me to iterate more quickly, I'd be more than happy to pay an extra few bucks an hour.
I cannot comment on future per node pricing at the moment, but we are currently working on new offerings that should improve both performance (CUDA cores/node) and $/CUDA core metrics.