Logary's pricing is transparent. You don't have to sign up to a newsletter to know what it would cost you to run it for your for-profit service. Licenses are yearly and subscription based.
You can load- and stress-test in a test-/staging-environment, for free, as long as that environment never serves production traffic.
This form reflects your selection above. You're purchasing a license for 8 cores, 3 developers for 2 years. This sets up a subscription, so that after 2 years, you'll be charged 444 EUR at the beginning of the year.