This is absolutely true, but for non-perishable items, even normal consumers can sometimes want to buy in bulk. I routinely get paper goods from restaurant supply stores, for example, because I have the space to stock up and store them, and because I'd rather stock up on a ton of paper goods every once in a blue moon than buy in more normal amounts and be caught unaware when something happens and I run out because I went through more paper towels than I was expecting. Also, groups of friends can definitely go in for single bulk purchases at these sorts of places, and if you're just starting out and know a lot of other young people in a similar situation, a small buying group for something like basic kitchen gear, plates, and silverware can work out really well.

That depends on what you're shipping and how you group it. Importantly, if you're shipping a knife vs. shipping a knife, some toilet paper, some paper towels, a bunch of sponges, and some assorted bulk food, the total amount that shipping is higher for the larger group of stuff is often way less than the amount you're saving cumulatively on all of it. Obviously, be smart and price compare, and take shipping prices into account, but I've been able to get pretty good deals on certain items fairly consistently

It depends where you're shipping to, and if you only order when you're getting a lot of things at once, it's still often worth it, even with shipping. I'd also avoid anything there which ships common carrier.