Yes, they will be cheaper from China. God knows how - if I wanted to post 454 grammes of beans to China it would cost a fortune!
Supermarkets are here to deliver a profit and not benefit the producer or customer. The price they charge is the best price they can get. I can go into one cut price "bargain" shop and buy 4 tins of tuna for 2.39 but the same goods are 3 tins for 3.00 in the local high street supermarket, and that's on (supposedly) "special offer". So where do they get their prices from and how much do they actually pay? Probably much less than the 2.39 the other shop can sell it for.
That is true for any product not just food. They beat the manufacturer down into producing the same goods for less and less money, yet end up charging more to make more profit.
The manufacturer then has to produce the same goods, but for less money - how does he do this? He cuts corners by using inferior raw materials or cheap imported components from China (LoL).
That is why we end up with crap low quality goods in our houses. The toaster that lasts 6 months; the cup made out of cheap porous pot; the car that rusts in 12 months etc etc.