Hi Martin
It’s a market, so I guess you’re looking for an intersection of what you’re willing to work for, and what the potential client might be willing to pay.
To calculate yourself an hourly rate, you could factor in what you hope to earn over a year / week / whatever, what percentage of time will not be billable hours – so how many hours a week you’re trying to earn that it. You’ll also need to allow for the costs of investing in and updating your kit and software, if you see this is a long term proposition.
Armed with an hourly rate, you could estimate how long you might need to do the work, and multiply …
Another approach is to consider what the customer may be willing to pay, and bid for something around that. You could always try a direct question – then decide whether to treat the response as a negotiating bid or as a ceiling. People vary very much in how the like to negotiate – so “reading” your customer right will be important.
You might also think about what quality they want, what alternatives to you they have (and what those alternatives might charge), how soon they want it, why they asked you in the first place (did they like your reel?) – and from that guess your negotiating position.
Good luck!