To be clear, it costs real money for regular people to give Reddit gold, but Reddit admins can do it for free. So it's a very strong signal from everyone but them, but just as meaningless as an upvote from them.
Good to keep in mind for the large subreddits and to put a grain on salt on those approximations, but even the subreddits hated by the admins show years-worth of purchases, it's also not likely to be prevalent in those like /r/aww where it's exclusively pictures of pets.