Well, I've used
Joe Rocket Alter Ego pants as a partially vented over pant, worn over LDComfort shorts. Love the full length zippers and the zip out mesh panel works well for venting. Stand up or just lift your butt off the seat and you get a really nice flow thru cooling effect. MSRP is $199. The zippers are a little light, but held up well. Two way zips also on the pants legs. I really liked these. Comfortable, good venting, reasonably waterproof and held up well. I crashed in the first pair and despite blowing out a leg zipper, they did the job and I had no injuries or abrasions. They don't do repairs, but did offer me a nice discount on a replacement pair. I eventually sold those prior to the '13 IBR to get a bit better armor with the MotoX pants. FWIW, the knee armor in the Alter Ego pants was some of the most comfortable and 'just fit right' armor I've ever had.
I've also worn
Olympia MotoX over pants that had a zip down wide leg panel that gave great flow and the panel tucked into the built in pocket below in the leg. Down side, these were physically heavier than the Joe Rocket and standard Mesh pants, upsides were excellent construction, heavy duty zippers, full length leg zippers and good armor. Super quick and easy to zip up the vents or put them down. I did have to have the knee armor pockets moved and the legs shortened/hemmed since my waist size resulted in far too long an inseam. I don't think these are available any more, but there are some others like them. I always felt like the knee armor in these was slightly off to the side of where it ought to be because of the leg zipper location. Never crashed in them.
Currently I am wearing a pair of Joe Rocket Phoenix pants. No rain liner, full leg zippers, decent armor. I carry some rain pants, which is a pain if I need to stop and put them on mid ride, but it what it is. Lighter, massively better airflow, not so beneficial in temps over ~95F, but less of an issue than a mesh jacket would be. These allow me to survive high humidity rides in the South.
Motorcycle closeouts has a bunch of stuff in the <$200 budget. I went cheap on the last pants and just got some rain pants cheap too. So far, I'm happy with them. I've only needed to break out the rain pants a few times, but it works and keeps me dry. Not a lot worse than a liner that you would need to strip to remove. And there is the real benefit of zip out panels, being able to change from out to in and back again w/o taking anything off. At least I don't need to get naked to remove the rain pants from over the mesh pants.