Do you really think the shirt sales are enough to cover their wages and signing on fee?
If you sold an extra 5,000 shirts (which I doubt considering the poor support you get), it may have paid for a month's wages.
When you signed them you had no idea you'd get into the cup semi final, so using that as a reason to finance the signing is nonsense.
If the club spent money on players knowing the debt had to be repaid, it's cheating. Whether the debt really did have to be repaid is something for for the court to decide, so I won't demand Cardiff's relegation yet.