Nope. Too many variables. Not enough information.
p.s. Just to clarify… it’s almost impossible (from my point of view) to even give a ballpark based on the information provided. There are too many variables. Everyone has different rates (mine is $50 which is pretty typical… even low perhaps unless you hire a student)… and every project is different. For instance… how complex will the design end up being? What are the project requirements? Would any custom work and/or integration need to be done to pull off those requirements? Etc.
Thanks for your reply David… Apologies I realise Ive been a bit vague ! I will have to put a concise brief together – what kind of requirements would I need to specify ? I am unsure how you would define the complexity of a design – do you mean in terms of whether its just CSS or if theres flash work ? Or perhaps if I supply the branding or someone else does the lot ?
When you talk about custom work or integration – what could these be other than creating the theme files ?
Any more specific pointers or examples you might have would be really useful !! 
Consider the cost for wordpress themes, as buddypress themes are wordpress themes. There are thousands of wordpress theme players around the world. Quick search on Google should give you some quotes.
You may need to add bit more ($100 – $500) to the quote you get for thanking designers to work for wordpress themes for buddypress. 
Thanks for the info ! Has anyone had experienced of commissioning designs through 99design.com ?
Your best bet if you want a fabulous BP design for a reasonable price (from both points of view) is to contact milo.
https://buddypress.org/developers/milo317/
@Marc: Requirements is a pretty vague term itself eh? A requirement could be as specific as “must support IE6” (which would have an impact on price) or as general as “must position us as an industry leader”. So requirements can be about business, creative, marketing, functional, technical or other goals.
The biggest things that would affect price however would be any functional components that BuddyPress doesn’t include out of the box (like Wiki, Document Library, Video Sharing, etc.). Although much of that can be done with plugins… said plugins may still require custom theming and/or some work on integration.
Complexity of design could mean things like Flash. If Flash work is required, that would cost more. If you require a logo or other branding, that could cost more. But I was more thinking of the complexity of the design in general.
For instance, this design of mine took almost a month of design, development, research and testing (it works in IE6 believe or not and is designed to have graceful text-resizing… as all my work is. XYZ is a fake name of course):
http://davidlewis.ca/solutions/
While this very simple “design” (a freebee for a volunteer organization) took only 2 hours from zero to WordPress theme (p.s. I’m not responsible for any of the horrible content like the logo sidebar… for instance):
http://www.hrsar.ca/e2cdev/
That’s an extreme example… but you get the idea.
And there’s also the difference between giving the exact same specs to a handful of devs and getting widely varying quotes back. 
Agreed! And generally speaking, you also get what you pay for And most people are also reasonable and can work within your budget. The scope and complexity may have to vary. But most people are willing (within reason) to do what they can for your budget. I’ve worked on projects with budgets as small as $0 and as big as $2,500,000… ‘back in the day’… before the dotcom bubble burst
also, two other big factors are timeframe (ie. know your launch date) and number of people involved. generally, if you’re the middle person/project manager who reports to your c-level folks, they’ll want to put in their 2 cents — sometimes even conflicting feedback (eg. http://www.youtube.com/watch?v=EgDWwahgsYk … ‘bigger logo but feel small’ type of thing) which will also affect your timeframe/cost/marketing budget. there really are sooooo many factors that play into getting an estimate for a scalable website.
And this sometimes can happen if there are “too many cooks”:
http://theoatmeal.com/comics/design_hell
LOL
Bookmarked “Design Hell”, thanks David. Will be showing that to new clients even before they sign on dotted line. That’s why there needs to be a contract outlining scope of project among other things. Upgrades, design changes after specs have been approved, and other add-ons need additional payments – unless it’s a pro bono project where you have the option to bow out of the project or hand it over to someone else
One thing I have found that works really well is to break the project up into many smaller pieces, so that the developer can give estimates on a granular basis. Then it’s just a matter of combining all the pieces together once they are finished.
I have also found a huge variance on what developers charge for their work. My practice has always been to search out coders with great reputations, and give them a small project to work on. I then look at the overall result of their work vs. the cost and timeframe it took to complete. This gives me a really good picture of how the individual coder works, and the cost – benefit to myself. If the coder does really well with the smaller project, then I usually propose more work in the future for the more difficult projects.
when you consider that a theme is nothing more than a set of functions, and a layout, the granular approach becomes easy to understand.
You may start out by saying I want a slider that does ‘x’ and I want to be able to control it via a theme admin panel. Have that project coded up, and then you can add that to any theme you choose.
The same concept can be expanded to all areas of the theme you are trying to ultimately achieve. The more functions you purchase, the more your theme can do.
What it also achieves by doing a theme in a granular mode, is that you can then hire out specialists in different areas at the same time. Meaning, you may need a js expert for some functions, and a css expert to put it together.
The hardest part of doing it this way, is finding the ‘master’ admin that is going to be in charge of combining all the code together, and keeping you updated in the future.
hope this concept helps you out.
Thanks for all the advice ! I will go away and put together a spec of exactly what I need and then look at contacting some developers! I hadn’t really considered that a theme might consist of additional functioanlity as well as just a ‘skin’ over wpmu/bp…
