This topic has been covered many times.
PBR is franchised and their metrics collection is not standardized nationally. Not even within the franchises. Sometimes exit velocity is BBCOR and sometimes wood. Sometimes metrics are denoted as wood--although no way for coaches to determine this when searching the PBR database, Same with the other metrics. Sometimes 60's are laser timed but most times not (equipment is not there). Lots of throwing metrics are recorded at indoor events; perhaps not a big deal but in my opinion OF velocity is not accurate indoors (too short of a throw).
PG is standardized nationally. While some metrics are collected at indoor events, they don't come close to the vast majority of collected metrics. They always user laser times, they always use wood bats, and they always follow the same showcase format.
As far as value is concerned, you'll get responses on both sides of the coin. If you have metrics that you think compare to top metrics nationally, you'll get a lot of mileage out of showcases. That was my son's goal and he used it as a way to make sure his metrics ALWAYS improved at every showcase he attended. And eventually his metrics compared very well with the top metrics nationally for his position. For kids like this, where getting an invite to the PBR Future Games, PG Junior National and/or PG National are goals, the showcases will help validate their personal growth. And in doing so, provides exposure for them. Just understand this is only one form of exposure; there are plenty of kids committing to big D1 programs who have attended zero showcases.
If you don't have metrics in the top 30% then I suppose a showcase (at PBR or PG) may not be the best use of funds except to provide some initial data for you to use and to improve upon. So not necessarily a waste. That is up to the player. Somebody has to provide the other 70% in the metric results!