Let's see, in NY commordity market, soybean costs

$6.4 per bu or $0.12/lb. The cost of most expensive freight transportation (i.e., with refrigerated cargo) is about $0.10/lb. The FOB price at Shanghai probably about $0.22 /lb or RMB 1.7/lb at most. The cost of soybean sauce will be RMB 0.034/ lb as one can make 50 lb of soybean sauce with 1 lb of soybean.
Now the market value of soy sauce is RMB 0.6/bag. This is almost 20x of profit.
Conclusion: trading soybean from US to China has big profit margin and profit potential.