You have confirmed that the garage exists and that it will be opened when certain conditions are met without further human intervention. The alternative would not come with a guarentee of the above. Just because the entire process is not zero-trust, does not mean it is not an improvement of the status quo.

If this were to become a recurring endeavour, you can introduce reputation into the system and a refund mechanism if X of Y funds required to unlock the payload are not happy with the contents.