I do the full-face helmet with the photochromatic face shield, so I don't wear sunglasses while riding.

When I dismount I like Oakleys or Maui Jims. These are likely outside of the OP's $100 price parameter though. Some Oakleys may be close to that, and all Oakleys are excellent.

The thing to remember about sunglasses is that you want them to filter out the UV rays, because these are hard on your retina. What you don't want are glasses that filter out bright sunlight, thereby dilating your pupil (to admit more light) and not filter out the UV rays. If that occurs, as with cheap sunglasses, you are exposing your eye to more, not less, UV by wearing the glasses. Not good. You want either polarized glasses or, failing that, glasses that otherwise filter the UV.

 

Pricey but made specifically for motorcycle riding.

7eye with air dam or air shield.

https://7eye.com/collections/fishing

For in the truck anything by Serengeti with the photochromic driver's lens. They are made specifically for eliminating eye fatigue while driving in a car. I've used them with a full face helmet too. Fantastic clarity in all sunlight conditions.

http://www.serengeti-eyewear.com/Tec...tochromic.aspx

 

I have spent a lot of money on sunglasses. If you do not have a prescription Walmart or other hardware stores sell 4$ safety sunglasses with 100% polarization. Bang for the buck, it does not get better.

 

Just got a pair of the Heatwave Visual VISE sunglasses, these are really nice.

They have different frame styles and you can even customize them.

And not expensive.

 

My favorite has become 3M Protective Eyewear with Gasket (http://a.co/1fSew5n)
They are comfortable, block air, are visually transparent, and are cheap, cheap, cheap.

I always wear a helmet with a retractable sun shield, so tint is not important to me, but they do make a tinted version as well.

 

For sunglasses, I like Revo the best. But you won't get them for $100 and they aren't really aimed at motorcycling.

They are the best sunglasses by far for off the bike though. The optics are outstanding.

 

No question...... Oakley GasCans....

 

Oakley straight jacket. If you're a veteran, you can get a discount on oakleysi.com.

 

Maxx tinted for the daytime-$20 and Igogs safety clears at Night-$19. The Igogs are available in bi focals which makes seeing the gauges a lot easier at night.

 

Wiley-X AirRage or Rayban Predator II The Wiley-X's are safer due to their impact resistance. They meet both ANSI Z87.1-2010 High Velocity and High Mass Impact Standards as well as OSHA 1910.133(b)(1)(1) Standards. But the Raybans are more comfortable to me. YMMV of course.
Never, ever get polarized lens's. If you're behind any sort of a face shield or a windshield the rainbows will drive you crazy.
Also, "Transition" lens's never transition fast enough or get dark enough IMHO.
Lastly, as others have mentioned; be sure they block UVA and UVB light. Very bad for your eyes if they don't!