I don't have any first-hand experience in getting milked 200 USD per day in Bhutan, but I see Europeans leaving reviews in those Airbnb and https://www.mfa.gov.bt/rbedhaka/visa-for-visiting-bhutan/ and https://visit.doi.gov.bt/help/faq don't say that being part of an organized tour is required to get a visa, which makes sense as tourists can stay up to 90 days in Bhutan (which would be a rather long organized tour). Therefore, I'm inferring that the information you have read is outdated.