10 days is not a big deal if it's just one shipment. It's a huge deal if it affects every ship that would otherwise have gone through the canal, i.e. 50 ships a day, 18,000+ ships a year. That's 180,000 extra ship-days per year. That's a pretty major bullet in an economy built on just-in-time inventory control.
Aside from the additional ships, you need additional containers, employees, etc. It also costs more in bunkers, etc. For JIT it wouldn't matter too much though. As long as it arrives on schedule it would be ok.
