The average marijuana smoker in Colorado will pay about $650 for the drug next year, according to Time.com. The estimate is based on a study by researchers at Colorado State University, who wanted to determine how much the state will collect in marijuana-related tax revenue.

The study assumes next year, 642,772 state residents—about 12.5 percent of the population—will use marijuana, now that it is legal in Colorado. Researchers estimate each person will use 3.53 ounces annually, at a cost of $185 per ounce. Residents can only purchase one ounce of marijuana at a time, the article notes.

The quality and price of marijuana, as well as how much a person uses, will influence how much a person actually will spend. Last month, one ounce of marijuana averaged $206 on the black market. The price is expected to drop once marijuana is sold in specially licensed stores, starting in January.

The report estimates that a 15 percent excise tax on wholesale marijuana will bring in $21.7 million per year. The state expects the tax will raise $40 million annually.

“As competition forces growers and sellers to be more efficient, margins will erode, and both wholesale cost and retail prices are forecast to fall,” the report states. The authors predict a “decline in the rate of growth of consumption as the ‘wow’ factor erodes over time, and any marijuana tourism begins to decline, particularly if other states follow Colorado and Washington and legalize marijuana.”