Harbor Freight sells their own brand of heavy-duty airtight plastic cases with pick-and-pluck foam inserts. Their brand name is Apache, and they have a variety of sizes.
The Apache cases aren't the same level of quality as Pelican or Storm, but they are still high quality while being significantly less expensive.
If I were going to be transporting expensive electronic equipment through the wilderness in the rain or through dust/sand storms I'd want Pelican or Storm, but if all I wanted to do is store some knives I'd definitely chose Apache.
I use an Apache case to transport my $400 laptop strapped to the back of my motorcycle.