Yea, good visors are expensive. My Shoei and Arai ones are about $65 usd each.

I would be a bit careful about using furniture polish on your visor. Some are OK but others can ruin plastic ... it will eventually get dull. Many guys here use Windex ... also BAD for plastic over time.

I use a product specifically for Plastic, it's called Plexus. A bit expensive but if you use it sparingly, lasts a long time.

Your Schuberth helmet may have an internal pull down tinted visor? I've had helmets with those, but the pull down visor is cheap plastic and scratches up badly. Soon, you can't see through it. I took mine out on my HJC. My older Multitec does not have an internal pull down visor.

On my Shoei Multitec main visor I use the trick I've used for 25 years. I put a strip or two of black electrical tape across the top of the visor. When Sun is low the tape mostly blocks most of the Sun. Works great for me!

But a clean, scratch free visor is essential. Here is how I get 4 years out of one visor:
1. Never wipe off visor when dry ... always wet with water first.
2. After fully wet, wipe off dust/dirt gently, rinse. Wet again, add a bit of soap and wash. Rinse. Dry visor with SOFT cloth.
3. Spray with wax cleaner product (I use Plexus) lightly. Rub in with CLEAN, soft cloth, polish up gently. Never hard as even ONE grain of sand or grit can RUIN your new Visor.
4. Do the same on inside of visor.
DONE.