The Goblet of Fire Clock Tower is available from Mills Fleet Farm (not local to me but in upper Midwest) for $71.99. Shipping is $9.99 but there is a 10% coupon that works: 10HOLIDAY19
The coupon expires today (12/7/19). With the coupon and shipping, the total is $74.78 (+ tax if you have a store in your state; no tax for me). I applied the coupon but then when going through checkout it disappeared and started giving me an error. I opened a new incognito window and checkout without any problems.
This set (unless I missed it) was not on sale during Black Friday or Cyber Monday. It works out to about 8.11 cents per piece, which isn't the best possible but it's a good deal for this set right now.