Gunnar isn't the only blue-light blocking coating. Most major lens manufacturers have equivalents (Essilor has Crizal, Hoya has Recharge, Nikon Seacoat, VSP Unity With BluTech...). You'd need to go to an optometrist to get prices, although, most optometrists in private practice usually only exclusively use a single lab, so if you want to cross-compare, you might need to go to many. You can always buy frames from a cheap place (coastal...) and then go to the optical for lenses. There's a huge variety in materials and coatings available that the online places can't necessarily match.
I'm a techy guy (and a radiology resident), so I'm literally on a computer for 12 hours a day. F.lux is a great start, but not everything can be so tweaked. iPads/iPhones need to be jailbroken to get equivalent tinting. I can't tweak the view-stations at the hospital. I also spend at least 2-3 hours in conference looking at a projector, etc. I have Hoya Recharge (I think) in my lenses, and I love it. It's made a huge improvement in my circadian rhythm and helped significantly with eye strain. I strongly recommend for those who stare at screens all day (most people in medicine that are tied to EMRs etc...).