MySQL vs SQLite on Amazon EC2
If you are concerned about the cost of iops, which are incredibly cheap in Amazon, then you are talking about a scale which sqlite will not be able to handle. There is no direct way to compare iops between two server types without benchmarking under your exact work load. Even then, i/o is going to be a function of how well your server is tuned.  Generally speaking, a true rdbms has several levels of in memory buffering to reduce i/o as much as possible.  Additionally, adding caching layers in front of the DB will help.

If you expect any concurrency at all, sqlite will not be sufficient.  It is really only good for development or embedded environments.