On what info do you base this on? Given a typical two sorties a week, you would need 500 weeks to get a single life fire sortie? It is not that rare.
Mind you, flying a fighter jet is also expensive, ie $10k’s per hour. Not all weapons are that expensive (gun ammo, dumb bombs, rockets), although guided weapons can be extremely expensive (100k to 1M).
In order to stay proficient you would need life fire exercises a few times a year I would think.
Not that it matters, I fly without weapons in DCS often enough: formation flying, air to air refueling, carrier landings to name just a few interesting activities.