Well, here's some useless injection:
Idiots around here throw 4 Par 56's on a floor mounted square truss section with a dimmer/power pack running a random patter. Repeat on the other side of the stage. The Asians around here pay $800/night for that crap.
For sound, they whine at me bringing in sound AND lighting AND monitors for $800. Go figure.
For me, I just come up with a flate rate and leae it at that. Something I can live with. If I went with the 10% number, I would be charging $3500/day. My old day rate(just me alone, gedar extra) was $2400/day. But people around where I live are cheap.
If people want a custom light show, it should be billed HOURLY for the pre-show programming(done BEFORE the day of the show).
What I'd do is see what the competition charges, and then stay competitive. If you've got better gear and skills, charge a bit more. You may not get jobs right away, but once you do and they notice a better product offering, you'll be good.