I don't know about starting again,but I might have held onto some of the stuff I've sold over the years.
Sold a 24-105 for £500 [which is what I bought it for brand new from Jacobs]
Sold my 300/4 Nikkor [which occasionally I regret - remember me, Dave!!!]
Sold a super sharp 70-200 2.8 and 2x TC combination
...but then I also remember why I sold this stuff. Moved from Canon to Nikon because of the 18-200VR [at the time, unique and highly desirable, and I bought one before I had anything to mount it on]; and sold the 300/4 because handheld the 70-300VR beats it for image quality - [no point having all that resolution capacity if your shots are blurred].
Still, right now - a D700, the longest lens I can get for the money and a 14-24. Way out of budget, but that's me..