Sorry, but from what I have seen, this "Black Friday" sale was quite poor. I only had 2 popups, one for an Event Building I had no interest in - but the 2nd being 50 forge points for 995 diamonds. What? 50FP for 995diamonds? What a poor, overcharged offer that is. 50fp is so easy to obtain, whether it is a prize from one of the GBs, or from a couple minutes spent in Battlegrounds - so to charge nearly 1k diamonds is very poor. Inno has made some poor decisions, such as permitting young Era city's be able to so easily obtain GB's from far distant Ages, so they can get the GBs that offer prizes (such as H.C, or S.C. plus others). And the diamond farms all over the place, would be considered an abuse of game currency in most games - except Inno created this scenario, and is silent about doing anything to fix it (i.e. stop letting diamond farms production be used account-wide).
If you want to do a Forge Friday (based on the American Black Friday), there needs to be value for the purchaser - not just a gold sink (well, diamond sink with this game). So, no clue if any of the other 'sales' had value or not - the one Event Building I saw might have had value for some people - but the 50FP for 995diamonds is absolutely bad value. (as poor of a 'sale' that these FP's are - I would not even want to know what you would consider a regular diamond cost for 50FP)