Organic reach - spreading the word naturally through your networks. You can ask your advocates - employees, partners, customers to share posts on your company's behalf. It helps their Thought Leadership as well.
The attached screenshot from LinkedIn ads, show you that you need to pay up to $23 per 1000 impressions. However, Organic reach is FREE!
Further, IMHO impressions from sponsored ads are questionable anyway. Instead, when your network shares your post, it directly ends up in their networks' feed.
Let's calculate the social reach you can achieve with organic reach. For example,
If 200 employees share your post, the potential reach on LinkedIn alone is 62,880 impressions even if you account for 20% overlap of connections among themselves.
To achieve the same with ads, your cost is $1449 per post. Imagine, if you could post 20 times a month and your advocates that can share that every time, your ROI is 20 times higher.
You can calculate this for your own company here.
The key to success in organic reach method is to make sure you it absolutely easy for your advocates to share across networks - automate it.