You'll also find "bundles" coming from less-well-known resellers at E-Bay for older processors, sockets and motherboards.
I would think the EOQ policies of resellers try to reduce surplus inventories of products, but the big boys all have warehouses and inventories. One might think that surplus inventories are more of a problem for the small players.
So I've even seen brand-new retail-box Sandy processors bundled with brand-new P67 and "non-Z" boards in recent weeks. "Memory-4-Less" was also offering a processor bundled with Intel Cherryville SSDs.
And what you find with these older models in bundles: Once you're no longer able to find a certain processor by itself at the Egg or Directron -- knowing that retail-box prices were always set by Intel -- the bundle prices can seem absurd. You might find a $350 Intel processor bundled with a $150 board for prices exceeding $570.
For new models, I can only pay attention to a "bundle" bargain if the items were in my initial build-list. I won't build a more expensive system with a motherboard not shown to be especially worthy in reviews, so I won't accept a bundle of anything less than parts I would prefer otherwise.
Now if it's a "low-end" system-build I'm pursuing -- say, for a family-member who doesn't game or benchmark -- when the user's existing system has "gone south" with no good parts replacement prospects, then -- sure -- I'll jump on a reasonably good bundle to finish the job.