The reason that IBM/Motorola stop being competitive was the cost of staying competitive was to great compared to the number of processors they hope to sell. By the time that Apple made the switch to Intel, they were the only PPC customers besides game consoles and mainframes that had different needs. Apple was only selling five or six million computers back then.

Now, Apple sells about as many ARM based devices than all of the PC manufacturers combined [1] sell x86 chips. Apple will be its own best customer.

[1] Apple sold about 230-240 million iPhones, iPads, watches, AppleTVs and if it start selling ARM Macs it will add about 16-20 million to that number.