I agree to selling old gear. It is a great way of funding new one (plus it is a good excuse too).
I am embarresed to say this but do I agree with you on the "good dinner after being hungry" comment ... Congratulations on the 5D MK III ... when it comes to selling my old gear I am very fortunate to have several colleagues in my office who are eager to buy my used gear ... recently sold the Sigma 150-500 OS, EOS-M, 22mm , 18-55 IS STM, EF-M adapter and a few other accessories, which funded the 100-400 L IS + 70D today.
... so I choose the trusty Canon 100-400 L IS and I also got the EOS 70D to get that little extra reach (also the sales guy made a really good deal) ... so now I feel a bit relieved from the GAS ... but that's only till the Sony a6000 releases. Isn't it great? Having sold my 5D2 I bought a second 5D3 and now I feel as if I had a good dinner after being hungry ... ( = GAS relieved ). I found out that for me the solution is to sell old gear (if and when I find a buyer of course) and get a new item. My list of old items has decreased though
Selling old or unused gear is almost as satisfying as buying new and shiny gear! I'm currently trying (not very hard I must admit) to sell my 7D. It's the only bit of kit I don't really need. I love it though. Kind of want to keep it just for the heck of it. I think I need to rekindle my love for it by actually taking pictures with it.
The new Sigma Art had been giving me GAS but it's taken so long to release (not really) that I'm getting over the urge. I seem to "look" for things to buy and now want a Samsung 840 EVO SSD to speed up my laptop. GAS cross contamination into PC equipment now!
+1. Selling old gear to fund a new purchase is very satisfying. My Sigma 150-500 covered half the cost of the bad case of GAS I had for the new Tamron 150-600.
On the other hand having someone else finance it is even better
I recently found that my old 70-200 2.8 non IS had moisture damage. My insurance company wanted a repair report from a reputable camera store. Their report stated it was uneconomical to repair and the replacement model is the 70-200 2.8 IS ii. My insurance said ok, so I have 2 new lenses in the space of a week
Unfortunately my mind has started to turn to acquire a 16-35 2.8 L...damn damn damn, it never ends!