[Minnewaska]

You should be able to get a helical tie down anchor for $10 or $20 US, but perhaps the $80 CA version is made of something more rustproof.

There is a great product for tying down aircraft on soft field, called The Claw. They work amazingly well, are easier to install and easier to remove than screws. If you're anchoring in sand, I’m not sure they’re the way to go, but if you can anchor in grass, they are excellent. Unfortunately, they only come with three anchors (two wings and the tail) and are a bit over $100US. On the other hand, you’d have spares or a traveling anchor. Just a thought.

 

[Minnewaska]

I suppose you could always set a couple of the claws and have a backup, if a line parted or one pulled out of soft substrate.