I've left some instances out. These are ones I tend to use. This is also only for us-east-1. Feel free to add rows in the comments.
| size | nov 2016 pricing | dec 2016 pricing | pct savings | monthly savings |
|---|---|---|---|---|
| t2.nano | 0.0065 | 0.0059 | 9.23% | $0.432 |
| t2.micro | 0.013 | 0.012 | 7.69% | $0.720 |
| t2.small | 0.026 | 0.023 | 11.54% | $2.160 |
| t2.medium | 0.052 | 0.047 | 9.62% | $3.600 |
| t2.large | 0.104 | 0.094 | 9.62% | $7.200 |
| m4.large | 0.12 | 0.108 | 10.00% | $8.640 |
| m4.xlarge | 0.239 | 0.215 | 10.04% | $17.280 |
| m4.2xlarge | 0.479 | 0.431 | 10.02% | $34.560 |
I think I am reading this wrong. Your Dec. prices are higher than Nov. prices but you have a savings listed.