If you're referring to TV advertising, showing a 30 second ad at peak viewing times can cost £200,000:
http://www.mirror.co.uk/tv/tv-news/x-factor-final-ad-breaks-2760401
Given that advertisers will want their ads to be seen many times, and they'll have production costs on top of the broadcast fees, a major TV advertising campaign will cost many millions of pounds.
Morrison's are desperately trying to save money at the moment, which is why they've sold off all of their 'Local' convenience stores and they're closing several of their big supermarkets. (The one up the road from me closes down in 2½ weeks time).
So it's unsurprising if they're currently cutting back on their advertising budget.
However they've still got enough money for this one which, even with the very small amount of time I watch TV, I've seen loads of times!