Revryan,
A number of excellent knives are available in the price range you have specified. Some of the best candidates, in my opinion, don't happen to be liner locks, but rather, lock backs. Don't overlook the Benchmade Ascent (in three sizes); although they are listed a more than $50, with the usual discount they are not too far out of your reach. Personally, I like the Spyderco Delica and Endura better. For something the size of a Delica but even better in terms of design and performance, I highly recommend the Spyderco Calypso Jr. Lightweight. I also like the Spyderco Wayne Goddard Lightweight a lot.
If you really need it to be a liner lock, I'd take a good hard look at some of the Columbia River Knife and Tool (CRKT) offerings, such as the Kit Carson M-16's.
A lot of people like the Gerber EZ-out. These are definitely in your price range, although they don't enjoy the cult-like following of Benchmade and Spyderco here in the Forums.
In conclusion, if it were me, I'd flip a coin for the Endura or the Goddard Lightweight.
David Rock
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AKTI Member # A000846
Stop when you get to bone.