About 60 million barrels of oil produced outside of the USA are bought daily.
At a markup of $30/barrel above pre-war pricing, the cost to Asia, Europe, etc. is $1.8 billion/day.
If a tanker costs $100 million, maybe about 15 tankers a day would have to be lost to Iranian mischief to justify not risking tanker passage.
Countries might simply buy tankers stranded in the Gulf off their owners, fill them up with oil, and sail them out under US Navy protection. US Navy helicopters might fly above to rescue crew members if necessary.
The tanker owners have debt payments and would be willing to sell at a fair price.
How did you arrive at the 15 tankers figure?