You are absolutely correct. For 20 years, faced with a free transfer from SAR or paying a couple of thousand pounds for a dedicated system, hospital managers took the free option. Basically they refused to pay until there was no alternative.
What you are doing is indeed better in many cases than no transfer at all. However the taxpayer is suffering a bigger hit and patient care cannot be as good.
The need for transfers has fallen due to developments in intensive care and to a degree the destruction of specialised units by politicians. Nevertheless I believe some 300 transfers a year do not occur because the NHS wants to save money. Some of these go by road to the potential detriment of the patient. Others simply don't happen. England and Wales.would be adequately covered by two helicopters and one fixed wing (ignoring maintenance)