Too true it is a lot of work, but customers are lazy and love a clean looking product.
The other market bonus is making it a gourmet mix. If you have baby kale or arugula or mizuna or mustard...radiccio, so many possibilities - many of which grow faster than lettuce if anything - they are buying it for the interesting "gourmet" taste blend. And you can tweak and tailor the mix to keep it interesting. And you should get a primo price for that "mix" vs a head of lettuce.
Even head lettuce gets a few minutes dunked in the washtub here to keep it fresh for the market - and will float away slugs or other bugs just by leaving it in water while you rinse out the tub. We wash everything (except tomatoes and peppers), it does wonders for appearance and most of all, shelf life for anything with greens. The farm is organic so we do expect to find a few critters in the lettuce and such.
Re: shade for lettuce, somewhere there's a thread where Oakley described how a shade garden was made to keep lettuce cool all summer - no idea where to find that now.