while i don't feel qualified to comment directly on pricing a FileMaker job specifically since i'm not a seasoned vet, i'd like to share what i've learned from other types of gigs that i do have a bunch of experience with such as custom AppleScript automation solutions, web design and general tech consulting. i am really surprised to see so many people around here so quickly point to charging an hourly fee. after about 5 years of working "freelance" my experience has been that hourly has been the least beneficial to me, and my clients.
right off the bat, you've got this idea of time attached to the bottom line hanging in the back of everyone's head. the client wants it done fast and you want it to take forever. not literally, but those feelings are there if even at subconscious level. i've walked away from more than a few jobs in the past that took me 5 hours to do and ended up saving the customer thousands. or websites for example...
let's say the auto mechanic shop and the antique store down the street both want me to build them a 3 page website. for which party is a website more valuable? most likely the mechanic will have his phone number and address up there, maybe a little info. not much money can be generated because of the site. but the antique store will likely use those 3 pages to showcase inventory, perhaps even some simple e-commerce. 2 sites, same amount of hours to create. i'd happily do both jobs but i'd not be at all ashamed to say that i'd be charging the antiques store a considerable amount more for the job. it's worth more to them and will make them money and is a worthy investment for them to make.
i've switched to a completely value-based pricing method and the results have been more money for me and happier clients. don't adjust your price to meet their budget. if you say "the price for what you want is $10,000." and they say "we only have $8,000 to spend." then you should answer "no problem, we can remove some features to fit your budget."
not only will you get the most for your talents but you'll likely have clients actually asking to give you more money. it also drums up repeat business. another perfect example is reusing your solutions. i've got really nice automation system for handling catalog assembly for a specific type of customer. it initially took me almost a month to complete and the original client paid me about $9,000 for it. they estimate it to be saving them about $8,000/month. i've gotten a few similar clients requesting similar solutions and i've been able to tweak that one system in a handful of hours just for them. if i was charging hourly i'd be really getting the shaft on that.
to each his own and this is all my opinion of course. btw, i got most of the info that inspired me to rethink my hourly ways from the book "Getting Started in Consulting" by Allen Weiss. it's the best $15 i've ever spent and his info is priceless for anyone working in any field trying to make a living on their skills. do check it out, you won't be sorry.