If you cannot afford to fly the real machine....well there is the problem.
Have the machines gotten too complex and too expensive....thus too few.
Is there failure in the grand scheme being caused by this?
If the Opposing Forces flood the sky with reasonably cheap and fairly capable aircraft with experienced crews flying them....at what point does that trump the few, expensive, less experienced crewed aircraft?
There are only so many Dollars (Pounds Sterling/Franc's) to go around.
Finding training solutions that closely duplicate the real thing and as accurately as possible reflect the reality of the real thing seems the only answer.
Lots of hours in a ground based Simulator that accurately duplicates the processes and procedures despite not providing the G Forces etc....has got to be good money spent wisely.
Taking a wander about the Highlands in a high performance Jet Trainer, but not a Typhoon, must also have some value.