3-4k is the normal range for a set of 4 + bleeding.I just had my 2015 650s in for service and Air Bag recall. They discovered my two front accumulators needed to be replaced. I did not even know I had a problem with them. But I can say I noticed an immediate difference in ride quality after they changed them. They were replaced under warranty - cost about $3,000 I believe.
Super strange they would only recommend two accumulators when the norm for these vehicles is replacing all 4 as a set 🤔