Some people would consider the new price of the 16-50 f/2.8 a budget lens. And it may be compared to the equivalents from the other players, but I wouldn't consider it a budget lens.
The point is the term "budget" is very relative. You may be a millionaire or a starving student.
I consider the 100mm WR Macro to be one of the best Macro lenses available, and at around $850 at the new price (I got mine for $400 in early March so I got lucky) is still a good value. I am consistently amazed at the images it produces, whether on digital or film. Here's a digital example I took a few weeks ago:
500px / Photo "B&W Flower" by Tyler Puckett . That isn't a true macro shot (not 1:1 anyway), so it probably isn't the best example. But it is a very good shot I think.
You can go cheaper; Pentax has produced many macro lenses over the years. You can also go really cheap: grab any 50-100mm lens (doesn't matter the mount, the manufacturer, etc), and hold it up in front of your lens mount backwards (the front of the lens pointing down the throat of the camera). You have a macro lens.