Ask HN: Real examples of price of PaaS vs. IaaS?

I am sure there are many people here on the Hacker News with experience with both PaaS and IaaS (vm's/physical machines in the cloud) for hosting of server applications. Since the pricing models of all these services out there can be really complex (e.g. AWS) to use for a prediction of your future expenses, it will be awesome if you would like to share an example of your experience, in which you moved from PaaS to IaaS or the other way around and how did your bills changed, accordingly. Thanks.