Tins are certainly more economical than pouches, especially with multiple cats.
Zooplus is fab for stocking up and you can buy a discount voucher to use for all your purchases all year saving you money.
The animonda carny linked to by kaffiene (great name) is a great grain free food, & certainly economical. Butchers classic is another brand to recommend.
I wouldn't feed Felix because of the low meat content and grain included as low nutritional fillers. Just like giving your kids fast food daily. Especially when there are good value alternatives.
There are good grain free dry foods available at zooplus as well.
Good brands include Applaws, Orijen, Purizon,Acana and Taste of the wild.
They may appear expensive at first ,but you should find your cats eat slightly less as the high protein satisfies them. Lower nutritional foods ie Whiskas /Felix require the cat to eat more food to get the nutrition required.
And not surprisingly the cat is soon hungry again.
Some foods also contain sugars, causing tooth decay. Check for added sugars.
Grain (maize/corn/wheat) is not needed by cats as they are obligate carnivores. So we are paying good money for something to pad out the food, and for the cats to poo out more often. Getting no nutrition from it and making the litter box stink.