The social media platforms have made advertising very affordable. Any business can now reach 1000s of people starting from as little as £100 on platforms like Facebook and Instagram. Whilst every penny counts in small businesses, this is still much cheaper than people think.
Bear in mind that advertising on LinkedIn is much more expensive than on other social media like Facebook or Instagram. This does not mean that it is worse value. In fact, LinkedIn can be a very helpful medium for Business-to-Business companies - finding people who do particular jobs or work in particular industries.