I disagree, for reasons I stated earlier. If Tierney was at Leicester or Burnley and doing well, his price tag would be £50m or £60m when the big guys come calling like the guy Wan-Bissaka that Man U are paying Palace £50m for. It doesn't seem unrealistic to me that to buy a player from Celtic, with international and Champions League experience in addition to whatever talents he has, should cost a decent whack.
And to suggest Tierney is just a decent SPFL full back is petty in the extreme.