One of good my friends runs his own bike part business and he's told me that the margins on many products are very low (Brembo being one - damn!). He runs his own business thus has a small buying power but he used to work for a local well known motorbike company and built up very good contacts - I believe he can access trade prices usually reserved for larger companies.
Based on the above I'd say if your starting off and don't know anyone in the trade then, from the sounds of things, you're not going to be able to access very good rates. Price isn't everything of course so if you really believe your custmer service is going to be sh*t hot, and you have plenty of knowledge in your field, then you could be on to something