Especially when we are talking about herbicide, we're not actually talking about something for which there is no alternative. Manual labour will work just as well (actually probably better because you can be more selective). Anyone who has grown a garden knows this. The question is, how much more expensive is it?
Just randomly googling, I notice an article stating sugar beet is 20.30 GBP per tonne. That's apparently 1.3 US cents per pound (gotta love google calculator). Sugar is trading at 16.7 US cents per pound. Apparently standard sugar beets yield 130 kg of sugar per tonne, which handily comes out to 10.0 US cents out of the 16.7 US cents per pound of the sugar.
I don't live in the US, but it's looking like the retail price is somewhere around USD $2.50 per pound (ha ha, got the price from Amazon). So the breakdown is $0.10 for the beets, 0.07 for the processing and $2.33 for distribution and packaging.
The amazing thing for me is that back when I brewed beer as a hobby in Canada, I bought bulk malt directly from the maltster. 55 pound bags delivered across the country only cost a couple of dollars. There is a huge loss happening somewhere in the middle.
I guess what I'm saying is that we are pinching the farmer more and more and more to shave a few cents off the price of our produce. We could double the production price and it still is an order of magnitude lower than the distribution price. Avoiding manual labour at potential cost of the environment seems insane to me. It would make much more sense to see if we can fix the distribution problem.