I have been asked to subcontract a wireframing project. I do not bill by the hour. What is the best approach to arrive at a fixed fee for the project? Budget is unstated, but the timeframe for delivery is about 3 weeks.
15 years as an independent consultant (IT), and 99% of the time I bill hourly.
I hate to go against your 'no hourly' constraint, but if it's a short wireframe project with no scope but expected duration of 3 weeks, aren't you trying to determine 'how much of my time will it take to complete the wireframe deliverables within the timeline'?
Of course, defining the scope of what the wireframe requirements / end result will be is useful - otherwise you are guessing. You might walk from the deal if you believe it's a 5 week project and they only have 3 weeks to do it.
If you wanted to try 'value pricing' - have your client determine what the value of the wireframe will be. My assumption is they will have no clue, since clients don't tend to think of deliverables in terms of value, but rather cost. My clients (Fortune 50 size) would laugh me out of business if I charged based on value.
Also, don't assume that you are the only resource they are soliciting either. What will your competition charge? What's the going market 'value rate' or 'hourly rate' for similar services?
The value of something is inherently determined based on how much someone wants what you offer. Either you offer your time, or you offer a product.
If you offer your time, it's a matter of how in-demand you are, based on how many other projects you have going on at the same time.
If you offer a product, it's a matter of how much someone is willing to pay for the final thing. Then competition comes into play.
Since both of the above you have mentioned you don't consider good enough means of measurement:
I'm not interested in competition. They can go to India if the want they cheapest brain surgeon
I do not bill by the hour.
You need to pick some other means of defining what you offer and how it will be measured. File size? Lines of code? There aren't many other options apart from the two that you have mentioned, which you aren't interested in considering.
I determine price based on hours. I personally would consider how long it would take me, multiply that by my going rate, and bill that. My hourly rate is determined by how many people want my time. Every time someone wants more time from me, my rate goes up a couple of dollars per hour. I don't think I'm being cheated because I solve the problem faster. If I can get it done in so many hours, and my time is considered to be of a certain value, then that is the value of the final product.
People hire me because I solve problems quickly. My rate is higher because I'm fast, so they cancel out. More people hire me, the higher my rate goes. I find this works really well for me, and It's my suggestion to you, because supply and demand determine how much I get paid, and I feel like that's a win-win situation for me and for my client.
Otherwise, why not just thumb suck a number and make an offer? If they say yes, great, of not, negotiate?
I'd say that depends on the requirements, the time you think it will take you and how much you want or need the project.
There is no objective guideline to come to a price. If all else fails, just decide what amount will make it worth your while.
By the way, a bit off topic: I think you should bill by the hour. Solves all of these questions and in the end it is the fairest agreement for you as well as the client in my opinion.