We all know about and suffer LBA (lens buying addiction) and GAS (gear acquisition syndrome).
These conditions are incurable, so we need a way to justify our spend with Family and Friends (aka photographic subjects).
Here is how you do it!
What was your spend on photography in the last 5 years less any income received (lets say ~$12,000 and call that S)
How many images have you kept in the last 5 years (not just taken) and are on your disk drives now (53,472 and call that C)
CPI (cost per image) = S / C = ~$0.22 per image !!
So the more pictures you take (and keep) the lower CPI becomes!!