I've run my company and been a freelancer before for quite a while, don't know if this is a proper answer but at least I can give some points to think about when setting the price level.

• Where are you located? What is the price level there for this kind of work?
• How many hours you have counted it would take to make the app?
• Do you think you need to make revisions to the app many times before it is ready?
• Count also all the time you need to spend in the meetings, emailing, phone calls, traveling etc.
• Does the client know what they want? Do they have a good plan which you need to realize or is there going to be a lot of design work and planning with them first?
• Do you also make the graphics and design or only coding? Is the possible graphic artist experienced in this or do you need to spend time to get the graphics done right too?
• How about the updates & bug fixes, are you agreeing to support the app after it's release? (Usually it's good to make an hourly rate for this after possible initial bug fixes have been fixed)
• Do you need to pay the taxes from the money you get (vat + personal income tax) or do they pay you as employee and take care of the personal income tax for you?

Now if you have plenty of work already and this is not a critical must-have job you should price it accordingly, high enough to make it really worthwhile.

If you really need it, you could make an offer slightly lower than other companies / freelancers would make, but only slightly.. it's not good to profile to the low-end.

It should be rather easy to find out the hourly salary developers get in your area and then make an offer based on that. When estimating the hours I tend to multiply that by 1.5 first as there is plenty of meetings, emailing and other communication that needs to be done on top of the "real" work.
And if you need to pay VAT + your own income tax, count those in too.

Also, in case the client doesn't have big enough budget but you need the job you could offer profit sharing on top of the paid work. This can work, but it's much more hassle and you get tied to the project even after it's release as your money is now depending on it's success.

I had a Z list celeb type ask me about building him a app as he had seen a website I built for a show he was in. As it was just a WordPress type frontend type App I told him I would do it for £500.

He got back to me a few days later and found someone who would do it free of charge!

Dave