I was looking for the cheapest octa core smartphone on Google and on 1949deal shop I have found Mlais M9. I think this is really the cheapest device with a really strong hardware. It has octal core CPU MTK6592M with 1 GB of RAM and 8 GB of internal memory. Internal memory can be expand maximum with 64 GB microSD card.
The screen is 5 inch OGS with qHD resolution and it has Gorilla Glass protection which is really impressive for this price range. It has really nice design and it is very slim only 7.5 mm. About software Mlais M9 comes with Android 4.4.2 operating system. And according to the Mlais it has very strong battery with capacity 2800mAh.