If this true, it was a very expensive mistake.
Let's assume that 10 people accepted the £100 offer (£1,000 = 1,200€) and the other 27 received the mandatory EU compensation (no extraordinary circumstances allowe in mitigation), 27 * 250€ = 6,750€.
Total so far 8,950€, then add on the cost of 'care' (hotac, meals etc.) and it becomes a big number, probably of roughly the same magnitude as the cos tof the extra 10k litres of fuel.