TFsource have also answered all our doubts here:
Q: Why offer C9 & Mint box pricing options?

A: Many of our customers have long known TFsource to be a great resource for high grade packaged Transformers. In an ideal world every Transformer we receive would be in a C10 perfectly mint box, with no wear or damage. However, the reality is that we often receive a large percentage of our boxes in mint condition, but a small percentage of our boxes have some noticable flaw to them. For those customers that don't mind receiving a less than perfect box, they may now elect to order a "C9" box, which if you want to open the toy or do not demand C10 case fresh boxes, this is a way to save some money. For those that have come to expect C10 mint boxes from TFsource, you may continue to order as you always have, but now you are stating that you would like a mint box.
Q: What's the difference between a "C9" and "Mint" box?

A:

Mint Box Defined: Generally speaking this is a box with no noticable flaws. This is a very subjective matter, and to some collectors, every box is flawed, but in general the amount of wear to the box, window and damage is very minimal to none. 
   
C9 Box Defined: A C9 box is still a very displayable box, it may have slight noticable wear, a kink, ding, minor fray to an edge, etc. The box is still case fresh, and unopened with factory sealed tape on each side. Click here for a C9 box picture 


Q: What about in the case of a pre-order from TFsource?

A: One of the added benefits of pre-orders is that if you preorder you will get the best condition of all of our boxes. The first to preorder, will get the very best box we get, right down the line. It doesn't guarantee you a C10 perfect flawless box that the AFA would rate C10, but it does guarantee you will get a better condition box than those who wait.

Q: What if I want a C10 mint box? Can I get one?

A: Yes, in this case please make a request with your order to receive a C10 box. We cannot guarantee our standards will be exactly the same as yours. Grading is very subjective, and even with a staff of veteran MIB/MISB toy collectors at the helm of TFsource, it's still very difficult to always meet the expectations of every collector. Know that if you request a C10 box, we will make every effort to profide you with the nicest box we have and if you are not satisfied, please email us and we will do everything possible to remedy the situation.