When I offered Aviva Express rapid tan alongside my usual Fake Bake, I charged £5.00 extra, but that was because (a) it cost quite a bit more to buy and (b) being a syrupy consistency I used more solution per client.
Since March this year I've been offering Sienna-x's Tonight's The Night rapid tan and charge the same as Fake Bake - purely because it costs no more for me to buy, and I get the same number of tans per bottle as Fake Bake. It's gone down a storm and several of my clients have now converted as they absolutely love being able to shower-off the colour guide before bedtime. These same clients were shy about trying Aviva Express over the last year or two which eventually made me convinced it was the higher price putting them off. I charge £25.00 for a single spray tan and £20.00 each if there's 2+ clients at the same appointment.
I'm not sure if that helps you, but I guess if you calculate any cost difference between your rapid/traditional solutions and work it into your prices, you'll be both confident and justified in your price list.
Good luck xx