I just wanted to tell you all about how I have figured the cost of my equipment. I have always said that the true cost of a lens is the price paid less the price returned when you sell or trade it.
I recently decided my 24-105 was redundant with a 24-70 in my bag, my 17-40 didn't get used much unless I set out specifically to do panorama shots, and my 100-400 was due to be replaced by an expensive large prime. I sold all three and a 430 flash that was riding around in it's bag unused.
Total cost for all 3 lenses and the flash after 3-4 years of very enjoyable use: right around 60 bucks. I even made a buck on the flash.
One thing an L lens does that a standard lens doesn't do is hold it's value. This is true of so many things- if you buy high quality items used, they have already dropped to the used price level and will hold there or increase with time if you take care of them. Even if you buy new, would you rather lose 10-20% of the cost of an L or 30-40% of the cost of a standard lens? Of course it is a bigger investment to buy the L's, but it is undoubtedly a better one, especially used.
I wonder-what would I have paid to lease those lenses for 3 years? 1 weekend with 1 lens might be more than I paid for 3 years with all 3. Thats the facts.
Anyway, don't take this as bragging about my salesmanship and ability to bargain hunt. I just wanted to pass on some advice and maybe help someone convince themselves or someone they know the L glass is worth it (it is SO worth it).