You may be looking at two different solutions, then. One to handle the audio and video, one to handle the keyboard/mouse.
Does it absolutely need to be wireless? Both HDMI and USB are easy to run over ethernet cabling with pretty cheap passive adapters, and it's the only solution that isn't going to have any sort of lag or quality loss. $12 adapters get you 150ft over ethernet cabling for USB, $20 gets you HDMI over 98 feet of ethernet cabling, and there are active solutions if you need to get HDMI farther. Drill some holes between each floor and hide the cable and that should work for you. Note that these don't use a network for extending, they use the ethernet cabling directly.
If it does need to be wireless, it's not going to be cheap, it's not going to be lossless, and it's not going to be low latency. There are various solutions, like WHDI transmitters (~30 feet through walls, maybe $170 for a kit), or h.264 transmitters (~60 feet through walls, maybe $500 for a kit). You may also be able to combined the h.264 transmitters with a powerline network to get more range (the ones that I have do wireless or ethernet, since they use UDP/IP). Both will add latency and reduce quality slightly.
USB is trickier, as wireless USB extenders are VERY rare. The few that I could find had all been discontinued, so the only option might be enterprise-grade USB-over-IP extenders that might work over wifi adapters (they're not tested over wifi).
Really, just drill some holes and run some Cat6 cable with some cheap Monoprice HDMI-to-Cat6 and USB-to-Cat6 passive adapters. This will save you hundreds (or thousands) of dollars as compared to wireless gear that will always be a really crummy experience.