In addition to that, stores will have frequent sales on fresh products because their short shelf life means they need to be sold faster.
Second most important thing to understand is that produce is usually sold by weight rather than by piece but not always...which can get confusing. When I was young, the signs for produce really confused me, often making me think they were more expensive than they actually were.
For instance, apples priced at $1.49 are usually a per lb price. Apples vary in weight, but often range between 1/3 and 1/2 a pound (lb is short for "pound"...it's a British thing.). So the actual price per apple would be fall in the range of 49 to 75 cents.
But then some some fruits and vegetables are marked "ea" rather than "lb". "ea" is short for "each". Our local store usually prices Avacados and Watermelons this way.
Third it's important to learn to check produce for quality. There are a number of tests from smell to texture to visual examination depending on the fruit or vegetable. Some blemishes are purely surface and don't mean the food is unfit for eating. Others are signs of rot. Some of the best produce deals are for produce with surface blemishes or just odd shapes, which don't change their taste or health value.
Fourth, know that the bulk price isn't always better. I stopped by Publix the other day and noticed they had the 2 lb bags of pears pictured above priced at $3.49, while loose pears of the same type were priced $1.49 per lb. Even without a calculator, it was clear that the loose pears were a better buy. ($1.49 x 2 = $2.98)
Often there are some savings to buying in bulk, but not everyone is going to want to eat through a 5 lb bag of anything before it spoils. Freezing, drying, or baking are sometimes options, but not always worth the extra effort.