Connect two monitors to two PC without HDMI connectors

I have two older monitors that I use at home for my PC. Now I got a Mac Mini so what to do? Sometimes I need to use Windows 8.1, sometimes I need to use Mac. Do I need to get more monitors? The answer is no.

Solution is to use two Plugable UGA-2K-A USB to VGA/DVI/HDMI adaptor 

website below:
http://plugable.com/products/uga-2k-a

When I need to switch, just swap the two USB.

I can buy a USB switch,  so I do not need to swap them, but I don't understand why it is kind of expensive.  

http://www.amazon.com/SIIG-SuperSpeed-Switch-Adapter-JU-SW0012-S1/dp/B005EHND30

https://www.youtube.com/watch?v=KviBmjC7BDg