Cheap and expensive are subjective. I look at the ingredients and figure out if it's worth the price.
Fact of the matter is, prices are a form of marketing. Companies know ppl think that expensive means "Quality" and that "QUality" comes with a high price tag. Which in some cases Quality does come with a price tag but the price tag doesn't reflect quality. Carol's daughter can sell $18 corn oil to ppl because they know ppl will attach quality with price. Granted Corn oil is like $2 or $3 for 16 oz but ppl see a nice name, a nice store, and a high price and think they are paying for a quality product. While the product might work for them... they overpaid.
People like to pay more because it makes them feel good. They feel like they have quality or like they can afford the "good" sh*t in life.