I work for a small business(~50 people) and we use Salesforce more or less across all business functions. I've been with the company for nearly 4 years,so I witnessed a lot. Salesforce is a fantastic platform,if used correctly. It's worth it. It does make sense to use it for a small business. Salesforce can be as big or as small as you want it to be.If you are small business with small needs,keep it simple and use it to track sales.If you are business with complex needs, do tons of customisation, integrations and etc.