We've heard of 2-4% performance hit in terms of performance using pyroscope on Node, but in practice, we've seen ~1% hit in terms of perf (Though we're not running high-performance systems where we're trying to eke out every bit of perf from each pod, so YMMV)
My favorite little anecdote that I like to tell is that the first thing people often see when they add Pyroscope to their apps is that it takes way less CPU than other signals like tracing or logging. It's pretty common to see logging taking 5-10% of overall CPU utilization.
The other 90% is usually spent doing serialization / deserialization (half-joking).