I can confirm that spiders waste a lot of food. I always throw grasshoppers into webs at my grandmas and they'll eat like 1/4 of it before they're like "meh".
Some spiders actually tear a hole into the body of their prey, then vomit digestive fluids inside. All the meat gets liquefied, then the spider sucks it out.
Grasshoppers are huge, though. I wouldn't expect a spider to be able to eat a whole grasshopper, even if it's not one of the ones that eats a liquid diet.
