When I tell the wife about the gear I buy and then sold while be able to upgrade for a song... she doesn't care. I hope this doesn't sound like boasting, but I figured like minded individuals can appreciate the following tale.
It began with me reading an article about creating a black background using nothing but a off camera flash. http://glyndewisblog.com/2010/01/19/the-invisible-black-backdrop-photography-technique/
I was so interested in trying it, I looked for a flash and I saw a really good deal on a 7 graded used 430ex ii flash from B&H. It was something like $125 but then there were some customer service issues and the price went down to $116ish. Either way, for a fully functioning 430ex ii, that is a heck of a deal. Yes there were scuffs along the body, and on the wide angle screen one of the notches was broken off, but the other notch was there, so it still came out easily enough.
That was about a year ago.
On Craig's List, a lady is selling off her gear because she is getting out of the business. She is selling a 50mm f/1.4 and a 580ex ii for $470. I offer her $450 for both and she bites. The 50mm's auto focus is just fine as it should be, and the 580 is in perfect condition save for velcro being attached here and there. But I might eventually use the velcro so it doesn't bother me.
I then sold my scuffed but fully functioning 430ex ii for $184. So the final price to upgrade to the 580 is $41. A steal right. Well... I also sold the 50mm for $300... so for basically taking into my possession for 2 days, I was able to upgrade from a 430 ex ii to a 580 exii for -34 bucks.
And I'm loving the 580. The feel of it is dramatically different. The recycle time with the same batteries as the 430 is lightening quick. I'm a happy camper.