We’ve slowly been working costs down as we go, and we have hosting meta down to around $1000/month on AWS – that’s with multiple tweaks over the last 6-8 months. When we started this it was closer to $3000/month. Really!
Before: $2,717 / month
After: $1,030.06 / month
Note that meta is deployed as “super enterprisey” in our testing so it is somewhat … overprovisioned. 
We could do better long term by doing long term reserved instances which could cut the cost in half, essentially pre-paying for multiple years of service.
Any other thoughts this far in @sam?