Yes, much more expensive to convert than if you had paid for the option. Appartently around £900 just for the parts needed (headlight units, washers, module and switches) and at least 5 hours of labour.
There's an interesting thread here on all of this:
http://www.e90post.com/forums/showth...non+conversion
If you check out the DIY thread for the conversion, you will see how tricky the process is and can understand why it takes so long:
http://www.e90post.com/forums/showth...non+conversion