57% is the common savings number by moving to a 3 year commitment on AWS. Many people are hesitant to commit to 3 year contracts, it's hard to predict usage that far. Consider we may be going into a downturn and you are now legally required to pay for today's usage. Seems like OP is taking on some (all?) of that risk? I for one would not want to be the one holding those bags today, given the near-term economic outlook.
To get towards the 80% figures requires a deeper understanding of a company's usage, processes, and code. These need code changes