So I saw this a few days ago.
I like making things, and these seemed like a great way to get parts so I ordered a pack of 2 from eBay. £3.50 delivered. 
They come apart quite easily and do indeed contain a neat little power regulator board and a 600mAh lithium polymer rechargeable cell:
I also ordered one of these from Amazon. It cost £0.88 delivered without a 18650 cell. With some very simple modifications, the 'disposable' charger can become rechargeable.
I'll post a picture once I've made the mod, and I'm also going to see if I can work up a little enclosure to 3D print.
Here we go - not the neatest thing I've ever created but perfectly serviceable. Here it is powering my Raspberry Pi Zero
And here it is being recharged.
