...or proof of the adage about a fool and his money.
Opteka 420-800mm f/8.3 zoom for Pentax, $129.99 with free shipping on Amazon.ca
Look at that minimum aperture... no, wait, look at that discount (was $499.99)!!
Heck, it's almost worth buying just to see how good/bad it is.
And in the also-viewed bar below, there are even more extreme variants on the same thing. I have the feeling that most of these are amateur refractor telescopes with K-mounts fused to the back end, but maybe someone has shot with them and can share?