$25 at Ye Local Rice Shop (aka, Pep Boys). First time doing it - albeit, I've done body work before... but this is different. Results - I must stay are astounding! I've seen the professionals on here with threads on the manual process and I'm also very impressed. If I had to do it a second time and had ample time, I might go that route. This whole process took me maybe 25 minutes or so per light with 8 - 10 of those minutes being cleaning and masking.
The 3M kit comes with a 3 inch or so drill attachment / velcro holder, 500 grit, 800 grit, and 3000 grit (I think) sanding pads. It also includes a foam buffer and rubbing compound. The 3000 thousand is the only wet sanding phase per the instructions. The process I think is self-explanatory for any gear head or shade-tree mechanic so I won't get into that. A 5th grade remedial student could figure out the sequence.
Anyway, this being my first non-new Subie, my headlights yellowing/scratching has been bothering me something awful. I can't say that anymore
I didn't notice anymore hazing in sunlight. But, driving at night, I noticed a tiny bit that my OCD self is not entirely happy with. So I may go buy some refined polishing compound and hit it again. Regardless, great results with this kit.
Below, are the requisite before / after photos...