I've worked delivering food at pizza, and Chinese restaurants for over 20 years. At this point. I think I've worked more in Chinese, then pizza. Here's what I've seen.
They get their food from other Chinese people who. All Chinese, and Spanish people I've met in my life are mostly the same way. They simply refuse to pay too much for things, and will haggle to the bitter end to accomplish this. They'll buy in bulk. And they'll tell you to go pound sand if you ask too much for your product. So basically the people they buy from have already got the best deal possible. And they all pay low wages, but give plenty of hours to their employees. So they have the potential to make lots of money, but have to work long hours for it. This also means they can save money, because they're always working, and can get what they need from their employers. Chinese cooks get free meals, and free housing. So the low pay isn't a big deal. But this allows them to decrease costs all the way around. As they're only paying for one place they all share, and one lunch/dinner they all share.
They buy their food in huge quantities, break it all down right away, and freeze it/process it for future use immediately. Everything, and I mean everything is made from scratch, with very few exceptions. Every piece of battered chicken was hand cut, and hand battered with homemade batter. Which starts with a bag of flour, or whatever they use. The owners, and their family all work too. So they need less employees.
Compare this to a pizza place. Where the owner is hardly there, they buy most things pre-made (like chicken tenders, or pizza toppings). And they have to pay their employees enough to all live separately. You can see how they can do it so cheap. Also. They even negotiate a better deal on their rent. They are the shrewdist of negotiators I've ever seen. I once had a Spanish friend tell me that I should always shop at Spanish places, because Spanish people refuse to pay a lot for stuff. Well the Chinese are the same way. I highly recommend you follow this advice to save money.
If you see a Spanish market, or a Chinese one. I assure you. The prices will be great. When I lived in Providence RI. I always ate at the Spanish restaurants to save money. They sold the food by the plate (actually a Styrofoam shell container). They would have 3 sizes at some places. $6/$8/$10 for instance. And a cafeteria setup with prepared food. Mostly stewed. Chicken, pork, beef, etc. And of course rice and beans. You could pick a few things, and fill the container. I usually spent around $6, or $8 and got enough food for two meals. Delicious homemade food too. Such a bargain, but it was worth much more IMO. It was a families old recipes. And it was amazing.
I know I meander a little, but I hope this gets the point across. Basically they're all working as a team to keep the prices low, and doing a lot of manual labor for small money to keep it low also. And they share expenses to save money too. Efficiency basically.
Edit: I forgot a couple of things. They use like a flank steak, and cut it by hand. Huge chicken breasts, also cut by hand. Pork is like big hunks they marinate, then put in like a slow cooker, might even be a smoker. It's a big tall cabinet thing. Gas powered I think. Basically everything is gas. And they hang the meat in there to cook. Then they cut it by hand after. Ribs are ribs, and done the same as pork. Shrimp/scallops are frozen boxes, from the South China Sea. It's really no different then any regular meat. Just bought in bulk, and broken down by hand. They usually use chicken thighs for the General Tso's. Big bags of rice. They use a gas rice cooker, and an electric rice holder. Pasta is usually rice, but some wheat. Bought in bulk, and they cook it themselves of course. All sauces made from scratch.
I should also add that if anything breaks. They usually fix it themselves, or call a guy that works cheap. Usually Chinese, or Spanish. But occasionally American. The fish they eat themselves for dinner is bought cheaply at an Asian market, or bought cheaply from a local fisherman. All vegetables come from Chinese vendors, or Asian markets. Very big too, and cheap. Bought in bulk. Some are canned, like water chestnuts. They cut their own grass. Work on their own car, or have a cheap local mechanic. Guys that moonlight after work, and such. We just had the gas water heater break at my job (I work at a Chinese restaurant right now), and the owner replaced it with a new one himself. This is how I live too, and it's how I can afford to live comfortably only working 35 to 37 hours a week. I just watch every expense, and don't waste anything. I actually am an audiophile, and have thousands of dollars of HiFi gear too. I do good by the hour though, and I eat at work for free every day. Well the 6 days I work a week. I work from 3:30pm till 9 or 10pm Friday and Saturday. And from 4pm to 9, or 9:30pm Tuesday to Thursday, and Sunday. I hustle, and am very good with the customers. And I don't buy coffees, and eat out everyday. It's a good job. Even if I had a family. I could just supplement it on the side with something, like Ebay reselling, and get by fine. There's more money in pizza, but it requires many more hours. This won't work everywhere though. I live in the Northeast, and in an area with lots of money. So I wouldn't necessarily recommend this job in Ohio, or Indiana maybe. But no matter where you live. I highly recommend watching every penny, and working less. I'm a very happy person with very little stress in my life. Peace to all! :)