I notice 100 shirt owners like me have taken out the same policy. So, average replacement cost for a tragic dry-cleaning mistake in which all 100 insured shirts are lost is actually €235.
Obviously, any insurance company recognizes me as a sophisticated customer, so they offer me a choice: they could preventatively buy and store shirt #185 today, if I should ever need it, for an extra €10, or add a policy rider to insure the €50 difference between the replacement price and €235, for an extra 5.
It seems novelty pricing can be quite successful!
16,836€ (183 sold)
But yes, that's the way to calculate it.
EDIT: Someone bought another one, so my initial total is now correct lol