Performance could be in play on high volume webservices, setting a lower value reduces the overhead caused by excessive purepaths.
The question mainly concerns the impact of that setting on business transactions. Do those numbers stay correct, or are there only x % taken into account when for example showing the number of requests for a specific BT.
It will never be through because you never now which % of transaction was handled. You alway will have some variations here. I rather suggest disabling some hard sensors from sensor pack to reduce overhead and leaving those that are needed + some custom sensor. We've got such high load enviornments and this is how we handled it.