A "low priced" stock, is a stock that is cheaper than what you determine its value to be.
The value can determined based on many factors including p/e ratios, price to book, expected earnings growth, dividend yields, cash buybacks, etc. The real value of a stock will always be up for debate, so ask someone knowledgeable that you trust.
So if I see AAPL at $400 and take a look at the appropriate numbers and think the stock is worth at least $5-600, it is low priced.