A Refurbished Macbook Pro with the same exact specs are all different prices.... Why ?

You have to look a bit further than just the front page. Such as the top right one is $110 more than the top center one because it has a 256 GB SSD. The center one is only a 128 GB SSD.

Edit: Of the two you added to your post, the cost difference is the graphics hardware. The slightly cheaper unit has 4 GB of VRAM. The more expensive one, 8 GB.

Without knowing where you're looking at these, it's impossible to answer.

Again, 4 GB of VRAM vs. 8 GB (looks like the same two you added above?).