Mt Spokane Photography said:
The risk of needing repairs is part of the acquisition cost, I don't know how to factor it in, but for a lens like this, it might be $1500 over 5 years.
I agree with the premise of including maintenance in whole-of-life costing. But do you really think an old Canon L lens in good condition would have a 30-50% probability of hardware failure over 5 years?
My experience with L glass is that it just keeps working, unless you drive a car over it... and sometimes even then.
It comes back to ensuring the good condition of the item you're buying so you don't buy up a lemon. That's impossible to do on eBay, where I've be bitten before with apparently perfect Zeiss gear. That's where used gear retailers like Keh add value.
Sometimes picking something up cheap is not really cheap at all...