Sure, the example is any company that
doesn't run a market, and any company where its marketplace is fungible with another marketplace. AirBnB may have four times the market cap of Vrbo, but their addressable market, both vendor and consumer, is the same set of people.
The monopoly that Apple controls is not Apple's goods, it's the control of the sale of goods of other vendors to consumers who have no comparable choice but to transact via Apple. The consumers are the people who would have to spend $1,000 to switch to a different market, and then have to re-purchase every good they'd purchased from the previous market.
It's not like Walmart, where the consumer can walk across the road to Target and buy the exact same thing at a similar price. Imagine if every time you wanted to switch which big-box store you shopped at they charged you a $500 entry fee and you had to re-buy all of your household electronics.
I would also, in a general sense, suggest that in the only obvious direct competitor market, Google does not exert monopoly power, because you can install F-Droid as an alternate marketplace. They are anti-competitive in other ways, though, to your earlier point.