CHICAGO (AP) — Black-market marijuana will be cheaper than legal medical cannabis, so when state-regulated retail shops open later this year, they’ll need incentives to get patients in the door. A trade show in Chicago gave retailers some ideas, such as cannabis-infused premium chocolate and informed employees to guide each patient to the most helpful cannabis strain. Illinois’ first legal marijuana is expected to be sold in the fall. For now, businesses are studying strategies of veteran players in Colorado, Washington and California. Marijuana Business Media President George Jage says most Americans prefer to buy from legal sources. Black-market prices are hard to track, though experts pointed to a crowd-sourcing website as the best general estimate for Illinois— about $350 an ounce for high-quality pot. Dispensaries will charge more due to a tax.