Last year, I mentioned on boarding a BA flight (they knew I had a Gold card) that it was my 60th flight on BA that year. Not only did I get champagne in WT+, but so did the Austrian lady beside me, who would otherwise have felt left out......champers all the way to PHX.
The incremental cost is bu**er all, the goodwill purchased is enormous. I have a nasty suspicion that the bean counters don't look at it that way, may their socks rot!