Speaking as someone who has seen the metrics on what you spend and what you get, if you spend a shit-ton you'll get... something. The only reason I sat through it is a PR person wanted us to pay $500 a month for three Facebook posts and a newsletter. We would then have to pay $200 ea. to get the Facebook posts promoted. When I asked her for a case study where they did this and what they got, she jubilantly exclaimed that they'd spent $1800 on Facebook promotions in a month and gotten 750 likes, 6 requests for proposals and 4 clients. She was psyched about this. We were kind of gobsmacked that she wanted us to pay $2300 for 4 clients.
If each client is worth a couple thousands, then I say it's worth it. But honestly, anyone with a little common sense can come up with a decent social media campaign. You're way better off taking the class than paying some lady (that might not even know exactly what she's talking about either). People in my city can't even use Adwords properly... A lot of towing and cleaning services targeting the word "Montreal" on google. Not really the most effective way to spend your money since I mostly see them when I google "montreal weather" or "montreal restaurants". I click on their ad every time tho and think "I just made you pay a dollar for nothing!"