If you want something sharp and solid it will probably cost more than a $100.
Typically only Gerber daggers are near-zero ground, and so have any kind of real sharpness to them out of the box.
However Gerber Mark IIs often have these serrations that are totally useless. The un-serrated wasp waisted ones tend to be expensive, and are not as sharp in the "waist area". A much better choice, that would be under $200, is to go on Ebay and wait for one of the numerous mint Guardian IIs to come up. Even the camo painted ones have a very good baked on finish that is quite durable, and they go for way under $200 depending on condition.
The sandpaper grip offered by the gray handled Mark IIs is quite extraordinary however (superior to the Guardian grip): Just that secure feel alone would be worth a lot me... But the Guardian II sheaths are always outstanding, while often the more recent style of Mark II leather or plastic sheaths are junk, even on some anniversary models, like the one below.
The Guardian II tends to have a stronger point, but may need a light edge touch up.
There are many other daggers out there, but these are the only ones that I can vouch for their sharpness and edge geometry out of the box. I don't know about the Fox or Spartan ones, but a hollow grind is no guarantee of edge finesse. It is nearly impossible to correct geometry yourself on a dagger, and do this consistently on both sides by hand: It has to be sent in to a professional sharpener if it is the usual dull junk.
Most will say sharpness doesn't really matter on a dagger, but in fact it is even more essential to its basic functionality, as explained by William Fairbairn himself. Unless you just want a wall hanger...
Gaston