They are 5th in luxury tax since it began behind NYY/LAD/NYM/PHI, paying approximately $55M (97% of which came before 2020). The problem is, fans got used to them being top 5 and more often top 3 for a long portion of JH's reign. I think that's why it's easy to rant about cheapness when he's still spending more than 2/3's of the league (and yes, a large part of it is due to the overwhelming revenue he brings in).
Also, the Sox have a tendency to not see these contracts through to their end, so the idea of all these players being locked up for a certain time period does ring hollow. All we really have is what is being paid out today. Who knows what the move will be tomorrow?