In my view the board should tell association members what it cost to investigate Marty. However, in the final analysis the board can refuse on some pretext, perhaps valid or perhaps not valid, and the ONLY way obtain anything the board refuses to provide is to go to court where you will either prevail or not.

If you don't prevail you have spent time and/or money for nothing. If you do prevail you have spent time and/or money to find out how much was spent on the investigation.

Are YOU prepared to go to court? If not, then you have no alternative than to simply accept whatever answer OPA gives you. In this case I strongly suspect OPA will tell you it will not provide the cost for the investigation.

Essentially, this same problem revolves around EVERY complaint/problem/etc an association member may have with OPA. If the OP answer on any question or issue is not satisfactory, the association member goes away disgruntled or goes to court.... those are the only options. If going to court, OPA has virtually unlimited funds for legal representation while the association member must spend his own money and there is no chance of recovering attorney fees even if the association member wins. Of course, one could perhaps file all the necessary paper work with the court and represent themselves without an attorney. Even if this is possible, there is a great deal of time involved.

I believe an association member recently sued OPA over drainage conditions..... and lost.

The question for you in this particular investigation cost issue is how badly you want to know and how far are you prepared to go in an attempt to find out.