Sometimes people use upgrades and add-ons intercha

Sometimes people use upgrades and add-ons interchangeably.

Depending in the sentence and context, it can be the same or different.

Depending on where you go to eat, a bake potato can be an add-on

Eating prime meat vs. choice is an upgrade

Same product, only better

Any of these deals can be either way

Whichever way it is, there will be plenty of non-shareholders very upset

We will find out

Keep in mind the standalone part. VERB can stand alone.

Add-on

As the name implies, add-ons are additions to current products. They're often labeled as accessories, and cannot stand alone. Plug-in credit card readers are a popular smartphone add-on, for instance.

The main purpose of add-ons is to provide supplementary functionality and increase the value of a product. When your customers' online activity indicates that a customer wants to use their current product for new purposes, such as using their smartphone to take credit card payments, then it's time to offer an add-on.

Upgrades

Upgrades do not focus on a different product, they focus on an updated version of the same product. You could upgrade from operating system 1, which was created in 2010, to operating system 2, which was created in 2015, for example. The product is the same, but the version is different.