Recently I've started sending some proposals to some possible clients. One of these new leads, is not a competitor but a company in the same city as one of my current clients, and in my proposal I was mentioning that I helped this client of mine achieve over X dollars in sales with my work (web design). My girlfriend read this and thinks it is not my place to disclose the amount of money I've help them generate — take into consideration that the site I made was from the beginning, so there were no previous numbers. Now I'm wondering, is it? I mean, I'm not telling an exact number, just something in the likes of "I help them make over $100k in sales with my services". Is this considered unprofessional? Or rude? Should I go ahead and ask this client if sharing am ambiguous number of sales is okay with them?
I'm a bit lost, any help or suggestions are appreciated