The league is the core competition and most core supporters prioritise that.
If there's any shortage of cash, most will purchase their season ticket, then cherry pick whatever else they can afford - and that's the largest issue we have - fans are approaching the limits of what they can afford.
Of course there are many who will buy a £5,10 or £15 ticket for a one off cup game, or £45.00 for a CL game against big name opposition, but the CORE of support (imo) are reaching the limits of affordability. It's not just the £5.00 for a ticket, it's other travel and parking costs too, and an extra 10 here or there might not be much to such, for many it IS an issue, and they simply can't do it for all the extra games.
As a conservative estimate, let's say it's just 15.00 per extra game - there's going to be about 6 FA cup / League cup games, and 3 CL games - that would be 135.00 extra for them, that's without any Wembley trips, or away trips etc. and 15.00 is being conservative (on average). They just aren't going to show up for all those extra games - and it's evident in the empty seats.
You just can't take a £15.00 special ticket price in isolation and wonder why it's still not selling - you have have to take in context of what 'extra' you're asking of fans. There's a very good chance that if our crowds are 10% - 15% down at some games, that 10% = 15% of fans are right on the edge of affordability.