Sawblade steel knives?

I recently found a very slick little knife made from a sawblade and I am hoping someone here can give some info on this type of knife. The photo of the knife does not show the thickness and the knife claims to be made of 4140 steel or similiar.

I know nothing of steels and was looking for some actual users of sawblade knives. Can anyone say how thick or sturdy most of these type knives are? I am not sure what type of sawblade these makers are using however the one I found looks nice. When I think of a sawblade I picture the very thin ones used on hand saws and can not figure out why they would use a sawblade?

Of course 20 dollars for an american made knife may be one reason they choose the material however just curious if anyone has had a similiar knife?

The knife I am looking at is in the link and they have some pretty nice stuff...
http://www.blindhorseknives.com/product-005.htm

Saw blade knife blades are made from the huge circular saws used in sawmills to take logs down to rough planks. They log 1000s of hours cutting and as a result are tempered like no ones business and make excellent knife blades. I would be surprised if 4140 steel was used to create the saws from. That steel is used to make climbing pitons for mountain climbing and are tough to break but not known for holding an edge. I have a Becker Knife & Tool Machax made from 4140 and they did a good job of tempering it but understand this metal is the devil to temper correctly. hope this helps a wee bit.

A typical steel used in sawblades is L6. It's a very tough, high-carbon steel. You can make some pretty decent swords from L6.

I am going to look into this a little more at a local steel shop. It is very interesting and something I may enjoy. I am also going to order one of the knives in the link just to get an idea of the thickness and weight.

I just finished watching a few videos online and discovered that there are many variations of heat treating and tempering steel. It is much more complicated than I ever imagined. Thanks for the input on this...