Morning, The forum has a third party lens review that is located here...
The kit lens is very good. I believe that you can also purchase a 2 lens kit with either the 50-200 or 55-300 lenses. The 55-300 is the better of the two, as Aegon pointed out. The kit prices are usually the way to go, since the lenses and body can be had at a reduced price as opposed to individually. I really do not know that there are any cheaper lenses for the price, as the third party lens vendors need to make a profit on each item. Pentax is selling a body with lenses to let you easily use the camera.
Sigma and Tameron lenses are also good third party lenses. There is a lot to choose from out there.