The cheapest I could find on ebay was around US$70 + almost the same in shipping costs and would take about 3-4 weeks to arrive.
I've got an 19" rail so needed the biggest size available - and that is the aluminium type.
I really wanted a dust and waterproof one but they are over $300 inc postage.
Been looking around the shops and on the Internet without any luck.
Then on Monday I had to go into Bunnings for a tool I needed.
While in there I had the idea of perhaps getting one of those tradesman soft bags as an alternative.
Anyway, walked over to that area and bang in front of me was a selection of aluminium cases.
Then on the top shelf I spotted a row of the sealed plastic cases - really tough ones that cost the earth on ebay.
I ended up walking out with the largest size for $65
It's a beauty with plenty of foam padding that you can shape to the camera and it accomodates the rail with half an inch to spare each side.
Water resistant, dustproof, airtight, and you can padlock it.
Thinking about a smaller one now to carry accessories.
Please note I have no connection with Bunnings whatsoever.