Let be carefull, it takes very little staff time, hence low cost to deal with someone who goes to A&E with a cold etc. The costs that are quoted are wrong, as they assume everyone who is seen at A&E has the same cost. There are no great saving to be had from stopping people misusing A&E, but their health may improve by seeing a GP as A&E have a limited skill set.
Most missed appointments have little cost, as most clinics are overbooked and would run very late if everyone turned up. Likewise with GPs, GPs also use missed appointments to catch on checking blood test results etc.