Halal is a bit misunderstood by many non-Muslims. Typically except for meat products all food products are halal, What would make them not halal is if they are processed with alcohol or have insect products added to them, that is nearly always dyes produced from the cochineal beetle
As for meat products it is almost always more expensive to produce halal meats as to be halal the meat must be from a halal animal the animal raised for slaughter must not be fed any animal by-products, it must be raised with extreme kindness and not crowded in small pens, not used as a beast of burden and the slaughter should be individual and out of the view of other animals, the slaughter must be as fast as possible and with minimal stress or pain.
There is no need for "Halal Certifications" there is no centrally recognized halal certification agency anyhow. A nation' s truth in advertizing laws should suffice. If a product is labelled halal the producer should be required upon demand to show proof it is halal. If they can not do so they should face criminal charges for false advertising.
As it is more costly to produce halal,the cost of such should be passed on to the consumer. If a person desires to purchase halal it should be labelled as such to reflect the reason for the higher price.