The true cost of a nulled theme is not $0. It is the loss of your customer trust, your search engine ranking, your payment processor account, and potentially your entire business.
It sounds tempting. Why pay $59 for a theme when you can get it for free? Opencart Nulled Themes
The short answer:
Your store looks normal. Orders process normally. But every customer who buys from you will have their card stolen within days. You won't know until banks start calling and your payment processor (PayPal, Stripe) permanently bans you. Hackers love nulled themes because they create a massive network of infected sites. They inject hidden links to gambling, pharmacy, or porn sites into your footer or product pages. You won't see them because they are hidden via CSS (e.g., display:none ). The true cost of a nulled theme is not $0