$27 sounds suspiciously cheap to me. If a ~5% hike in price was all it took to save the planet, why all the angst?
I suggest that carbon offsetting is largely a fraud and the price is whatever the people will pay. That is why there is so much variation in the price. Different people are willing to pay different amounts. Personally, I stopped paying offsets and now I put that money, and a lot more, into capital equipment to lower my emissions. No middleman %, and no chance of fraud. BTW the offsets I was buying had a 20% retail markup and who knows how much wholesale markup, the vendor did not want to talk about that.