I think the Wii U Pro Controller can be found for around $20 eventually if you keep watching cheapassgamer.com. I actually think it's been $20 at some point already.
All I ever see it for is 50$ if I am going to spend that I would rather buy more DS4s that would get way more use. lol. I would buy a pro controller for 25$ if I could find it (new)
Using Google a pricing error apparently had Wii U Pro Controllers at $10 at Amazon. $20 one week at Sears, and $30 one week at Best Buy. Just skim through the deals page at cheapassgamer once a week and you'll probably find it on sale somewhere down the line.