Have you ever wondered why it cost $50 to get a pepperoni pizza delivered via DoorDash or why that Instacart bill seemed astronomically high? It's not just because inflation has increased food prices. Online delivery apps and the restaurants that rely on them also find ways to stuff fees into your order that are not always transparent.

Consider an order that I placed for a delivery of two Subway sandwiches. Uber Eats charged me $25.25, including the cost of the meal, a service fee, delivery charge and surcharge for placing a small order — a 91 percent markup compared with buying those sandwiches in person.

In a separate experiment, I found that some restaurants charged more for some menu items when you ordered through delivery apps. The Family Feast value meal at Panda Express cost $39 in the restaurant but $47.10 if you ordered it through DoorDash, Grubhub or Uber Eats. That was before paying additional service fees. Restaurants sometimes inflate menu prices to cover the commissions they pay to the delivery apps.

The next time you're deciding whether to order delivery, be aware of what it might cost you. Take a look at the bill and compare the cost of items in the app with what those menu items cost on a restaurant's website or at the grocery store.

The true cost of using a delivery app might compel you to use the phone to order takeout and pick up dinner yourself, or you might decide the delivery cost is worth it. Either way, you'll be better informed.