For a start you save 18 x 6 weeks annual leave = 18 x $10000. 18 x 4 x sim checks per year. 18 x EPC courses per year. 18 x CRM recurrents pet year, 18 x uniforms per whatever etc. etc.
FL610, you are quite right on the principle of on costs although your figures are misleading.They say that's worth about 20% cost on top of wages, so if 18 pilots go and they were getting a total of $144,000 per month that is a saving of $28,800 which out of the total pilot cost is a 3% saving.
A saving: yes.
Big dollars: no
22% saving: not in dollars
22% saving: yes in pilot numbers.
3% saving: yes in dollars