As Kengo stated, go by your hourly rate and then figure out how long it'll take you to perform said services. You could also offer two different levels - basic & complete.
Basic would be a vac, wipe-down with Meg's QID, & the glass.
Complete would add shampooing, cleaning everything with something like Meg's green APC, & finally treatment of leather & vinyl with something like OPT Protectant Plus.
Kind of on topic:
One thing I see people do that's kind of a pet peeve for me is "talking about" all the different cracks & crevices, cup-holders, vents, etc. that they are going to clean. IMO, those places all fall under "cleaning vinyl/hard surfaces". People list out all these different areas they are going to clean and to me, it's just repetitive. For me, I break it down by carpets, leather/upholstery seating, vinyl/hard surfaces (which is dash, door panels, etc.), headliner & glass. As I'm getting ready to re-do my website, here's a rough draft of what mine will look like:
Basic Interior Detail
Thorough vacuum.
Wipe-down all vinyl/leather/hard surfaces.
Glass cleaned to a streak free finish.
Complete Interior Detail
Thorough vacuum.
Shampoo all carpets & floor mats.
Clean all vinyl/hard surfaces and treat with a water-based (non-greasy), low-sheen UV-protectant.
Clean all leather and treat with non-greasy UV-protectant or conditioner (depending on type of leather).
Wipe-down headliner.
Glass cleaned to a streak free finish.
Anyway, that's just my little interior rant. It's worth what you paid for it.
