It's a bit of a red flag that they sell their highest plan, 600kg a year, as "approx. 100% of a global average footprint". While that's probably true, the median human does not fly. A one way flight London->New York generates almost this much per passenger.

The mean emissions of those willing to spend 600 EUR/year to offset their travel are going to be at least an order of magnitude higher. You're better off feeling guilty and reducing your travel by 10% (in terms of personal emissions).

I do admit it's tricky, because if everybody is scared off by the true price tag (my lifetime emissions as an Australian would easily be $500k), the technology will never get a chance to get economy of scale and lower prices. That's really what you're paying for when you sign up for the plan.