Weโve slowly been working costs down as we go, and we have hosting meta down to around $1000/month on AWS โ thatโs 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 โsuper enterpriseyโ in our testing so it is somewhat โฆ 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?