Depending on where the company goes to get this done, the cost will probably be between $3,000 and $7,500 for a plan. Then the plan must be implemented. Where does a company go to get this done? For smaller businesses, it's best to avoid larger ad agencies; those with 50 employees and above. They'll want to work with big marketing budgets, say, $500,000 at minimum.
It's also better to work with an agency that specializes email list in the b-to-b space; they understand the integration referred to above. While it's handy if the agency is local, it doesn't have to be. It's more important that the agency is a good fit for the company. Another alternative is to contract a good b-to-b marketing consultant to do your research and draft your marketing plan. But have the second step lined up, too.
An agency who can implement the plan, ideally a smaller agency specializing in b-to-b marketing. Check their work and get referrals from their clients. Whatever route you choose, make sure the firm you choose is very knowledgeable in the online space. Today, almost all marketing in the b-to-b space occurs online: information gathering and downloads of white papers and how-to's; organic search results, online ads, web engagement, SEO, email marketing, press, articles, etc.