Shipping your products by plane is much faster than an ocean liner. It’s also much much much more expensive.
Sometimes people will ship a few units by air (and the rest by sea) because they need their product by a certain deadline. Maybe you have a convention? Most likely it’s because you think you’ll run out of inventory by the time the ocean liner arrives. No one likes being out of stock on product when there are potential sales to be had.
I did air shipping once, on my very first batch. The ocean liner wasn’t going to make it by Christmas but I still wanted some copies to pass out as gifts. So I air shipped 50 units via DHL.
Air Ship 50 Units $1260 1 Week
Ocean Freight 950 Units $2075 5 Weeks
So yeah, it’s pretty damn expensive. But if you have a smaller-sized game then maybe worth looking into.