Like with any business service, there's no one-size-fits-all cost for marketing and sales. The amount varies heavily depending on the size of the business, its annual sales, the industry involved, and even how much the competition is investing in the same field.
For some companies, the costs can be quite modest, or even involve training people in-house in the practices involved. For others, it involves hiring dedicated marketing teams and consultants. It's also important to consider how much you need a digital presence, direct mailing services, or something completely different. Each service can cost a varying amount of money.
Sales can often be developed in-house, but you will need to make sure that your team is adept at 'sealing the deal', and turning a lead into a successful sale through strong knowledge and a good attitude. It can also be useful to offer commission schemes and bonuses to encourage sales personnel to work more effectively.