If you're talking in terms of service-based work (freelancing, consulting, etc.), then ALL of sales should be based around the value you're creating for the client. If I build a new marketing funnel for a client and they see an extra 100 leads per month — assuming their standard conversion rate...
The key skill sets are determined by whom you are targeting for training. Customer acquisition channels will also be determined by whom you are targeting.
I think you're looking at this the wrong way. Your customer acquisition cost is not something you should benchmark against other businesses. Without knowing more, like your short and long-term goals, it's impossible to answer. Two companies with similar business models may have different answers...