[tianjinmac]

I recently bought 2 adult and 2 child tickets during a Finnair "Campaign". I presumed this would be at a special price. I paid 29960 RMB (around $4000) for these "Campaign" tickets. When the "Campaign" period ended I checked the price and found that the same tickets for the same flights at the Regular Economy Saver rate would cost just over 25000RMB (around $700 cheaper).
I contacted Finnair saying that I had been misled by the phrase "Campaign", maybe unintentionally, and asked them to reimburse me the difference or give me a voucher for the amount for my next flight. I have been spending $4000 twice a year for the past 4 years with them.
They just said that the "Campaign" tickets were non-refundable, non-exchangeable and they could do nothing.
Is this not illegal advertising? Or is an airline free to mislead people to buy tickets in the belief that they are getting a special price when in fact this "Campaign" price is considerably more expensive than a regular price that can be released as soon as this sales period is over?