Magik's mutant ability is teleportation. The magic came through her tutelage by Belasco, AU!Storm, and eventually Strange.
Wanda is a complicated case, since whether her magic is tied to her mutant power has varied from writer to writer. But she wasn't any
good at it until she started learning under Agatha.
John may have been descended from a long line of sorcerers with a predilection for ceremonial magic and insanely bad luck, but there has never been any indication that his powers
came from that heritage. In fact, given that his creators come from an old-school hermetic tradition, magic in his book is almost
always something you learn, not what you are.
Steven isn't even the first Marvel magician trained in Tibet... that honor goes to Anthony Ludgate, aka Doctor Druid (Eventually. It's a strange story
).
The only time the "price" of magic gets mentioned is when Strange has to pay it. Seriously.