Northern's FEL and Hoe are US made, so there is no cost advantage. Since the implements are more than the tractor price, it drives that percentage much lower. You made an objective evaluation, and that is all anyone can ask. You could purchase the Jinma FEL and Hoe, and save some money on them, but they are not as good value as the tractor is. The FEL is slightly less than US made one, and the backoe is probably around $3K. There is additional issues to deal with, though. Again, not an apples to apples comparison.
In reality, the chinese tractor sales are not taking away from new big 3 sales. While some people might brag it up, that you can buy two Jinmas for the price of a big 3, in reality they were probably not close to allocating that much money to a tractor. The 2nd tier, Kioti, Branson, Long, etc are the ones nipping away at the big 3. Most of the people that I know, that are purchasing Chinese, are doing so instead of buying used or grey, or alternative to renting.