It's a great proxy for cost, but price has more to do with availability than with cost. I'd expect price to go up a lot more than 1/3rd, especially if this drags on.
Right, price is driven by supply and demand. If your ships have to travel 4/3 as far, you have ships available at 3/4 of the previous rate, so the supply of shipping went down. Demand didn't, so the price goes up.
If any Norwegians are reading, which are shipping nerds by virtue of geography, speculating in this market is essentially why John Fredriksen, the Warren Buffett of shipping, is rich.
Shifts in ship availability causes waves of bankruptcy, and either gluts or shortages (whatever happens to be most inconvenient at the time).