Reddit gets pitched in B2B threads as a cheap way to reach people who are already talking about a problem. My hunch is the cheap CPCs come with a catch: the audience is big but the targeting is coarse, so you end up paying mostly for curiosity clicks unless the offer is very specific.
A fair test could look like this. A SaaS company puts $1,500 a month into two or three ad groups aimed at subreddits where buyers actually argue about the tool category, with a demo booking or lead form as the goal. Judge it on cost per qualified lead against LinkedIn, not cost per click, because CPC is exactly where Reddit looks best and tells you least.
My guess is it works for narrow technical products and fails for broad ones. I'd like to see whether anyone has data that points the other way.