We're a one-man shop, so the cost savings made sense in the long run. I already use SSDB and Redis in production so I'm very familiar with supporting it.
A one man shop with paying customers shouldn't spend time on optimization, unless it's just for fun.
If I'm a customer - I'd rather see more value added functionality, rather than cheaper data storage.
But that is my opinion, hope that your customers appreciate you spending time on this.
A) you first need to run the service to get any customers
B) this might take long
C) you maybe don't want / can't get VC money at this stage
D) you maybe are not the most advanced dev who can properly utilitize s3 from I/O perspective, getting you to higher costs than possible
E) there might be a time period between introducing the service and getting traction which yields enough feedback, so you can start adding more business features
F) when you are burning your own money, you are more senstive to the cost side - which is not ultimately wrong
Just my 2c
In fact, adding another component to optimize the cost is adding another point of failure.
Which ends up being back to - purely cost optimization of the initial cost optimization.
It seems like the whole product is focusing on cost optimization. I suspect that the OP would be better off making money by doing cost optimizations for third parties.