Compensation not linked to ticket price
The fact is that passenger compensation is completely unrelated to how much a passenger pays for his/her ticket. Whether you paid £30 or £300 compensation relates to the impact a delay or cancellation has on your life - missing a family event, missing a critical meeting, not getting back to take care of your relatives/children.
Airlines are insured for these eventualities and such compensation provides an obligation to treat your passengers fairly (regardless of business model) but just as importantly an incentive to avoid long delays and/or cancellations. Clearly a unprecedented shutdown of airspace is probably not foreseen in these rules, but are we suggesting that passengers should be abandoned?