Zero Tolerance makes quite a number of sturdy tactical folders with 3.5 to 4 inch blades for $300 or less. The 0200, the 0300, the 0777, the 0600, the 0560, the 0550, the list is awesome and long.
Spyderco also makes some fine 4" folders, like the Endura, the Military, and the Police.
Benchmade has a couple that don't suck badly, but the only on in that size range that I own is a 940-1, which sounds like it might be a little small for your tastes.
You might give Cold Steel a look, the American Lawman is well reviewed but again, it might be a little small for your tastes.
I'm sure SOG has some in that size range, too, but in my experience, they rattle after very little use and it bothers me.
There are Sebenzas, of course, and Striders and Microtechs, but they are out of your stated price range.
If you aren't a steel snob, Kershaw and CRKT make some decent knives in that size and they are well below your price point. Just a thought.