After two years of heavy duty farm work, one of my trusty LaCrosse SPOG boots has sprung a leak and suffered a sizable (8cm) tear. A younger me would've thought nothing of (in fact, would've been excited about) dropping $150 on a new pair of the same model, and this sentiment has been echoed by all the well-meaning people around me. However, current me (who I think future me is going to be thanking a lot), instead spent $7 on
some repair adhesive. It took me all of 15 minutes to wash/dry the boot, rough up the surface with a wire brush, clean with rubbing alcohol, stick some backing tape to the tear, and apply the adhesive to the leak and the tear. I'm guessing I used 5% of the tube to do this repair, and if this stuff works like it should, that's a pretty good ROI! Plus, I love doing this kind of meticulous work with my hands.
The product can also be applied to anything else made of neoprene (waders, wetsuits, drysuits, cycling gear, etc.)
One warning: this stuff smells like it could give your unborn grandkids health problems if you inhale too much, so be quick and/or use it outside.