I have a Kershaw Vapor 3" plain blade. It looks a lot like the RSK-1 from Doug Ritter which I can't afford. The vapor I have is very good and keeps the sharpeness for a long time.Also the blade looks a lot the same. I know that the RSK-1 must be better but I don't have one to compare it to the Vapor in everyday use. Is the RSK-1 so much better that it is worth the difference in price and in which ways it is so much better?

Knives have diminishing returns. IMO, a $30 knife is probably about twice as good as a a $15 dollar knife, but a $140 knife is not twice as good as a $70 knife. That isn't to say that the $140 isn't a lot nicer than the $70 knife, but it probably isn't twice as nice.

Is the RSK worth the price? If you can afford it, yes. The RSK has some pretty good blade steel, and Benchmade's Axis lock (which I really really like :)) But if you can't afford it you can't afford it. IMO Kershaw makes some pretty nice knives at some pretty good prices.

Here's a review of the Vapor. Looks like a solid knife.

http://www.cutleryscience.com/reviews/vapor.html

I EDC the full size Kershaw Cyclone and absolutely love it.

There are a couple of knives that I consider "best bang for the buck in their price class".

In the $20-ish dollar range:

The Vapor is one of those.
The Byrd Meadowlark and Byrd Robin are two of those.
The Benchmade Pika is one of those.

In the $50-ish dollar range:

The Spyderco Native and Spyderco Delica are two of those.

I don't see much NEED to buy anything much more expensive than that. Of course you may WANT something more than that, which is perfectly fine, but for everyday utility and normal use I don't think more is a requirement, it's a luxury. If you are a collector, or have day to day tasks that need the absolute longest lasting edge or some other special trait, then your NEEDS will vary from mine.

I have looked at, and drooled over, many knives more expensive than this. But in the end, 95% of the time I would set them down again because I couldn't justify the cost given my intended uses.

+1 on the Spyderco Native. Probably as good a "bang for the buck" as you're going to get (for <$40 at Wally World last time I checked). Still, if it's in your price range, the Benchmade axis lock models are really stout.

In the interest of full disclosure I do own a Native but I normally EDC a fixed blade.

Sorry, but I'm just not convinced. I have purchased waaay too many folders searching for one that I like. I have Bucks, Gerbers, Kabars, and several others that don't come to mind right now. I was never satisfied until I got my Doug Ritter RSM Mk1. Between the fullsize Mk1 which goes camping with me, and the min Mk1 which I EDC, I have finally found the knives I've been looking for. The axis lock is amazing. It opens and closes like its an extension of my hand.

Folks can spend a lot of money trying to find the gear that meets their needs. In the case of the Rittergrips the price is money well spent.

By the way, its the same with the Mk3. Buck, Gerber, Moras, Becker, and then finally the Mk3.

Thank you fellows for all the answers. It really helped me.