Halal certifier Mohamed El-Mouelhy sues anti-halal campaigner Kirralie Smith for defamation, page-19

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".....The Australian Food and Grocery Council says that “the costs of certification are highly unlikely to influence product pricing, and so consumers do not end up paying any more for certified products”....."

http://www.sbs.com.au/food/explainer/lowdown-halal-certification

Does halal certification make the products I buy more expensive?

Retailers obtain halal certification in order to increase sales and profits. While obtaining certification is an extra cost, that cost should in theory be compensated for by increased sales – especially exports. The companies concerned would not be forced to raise their prices as a result: The Australian Food and Grocery Council says that “the costs of certification are highly unlikely to influence product pricing, and so consumers do not end up paying any more for certified products”. Some retailers have stated that the higher volume of sales generated by halal certification has allowed them to provide lower prices to all customers. Keith Byrne from Byron Bay Cookies, for example – a company that faced strong criticism for its certification – has described halal certification as a low-cost investment similar to obtaining gluten-free or vegan certification and says it has helped them to keep their prices stable.