DENVER — In the first month of legal recreational marijuana sales in Colorado, retailers who shared their proprietary data with NBC News say they have collected $1.24 million in tax revenue.

Half of the state’s 35 licensed recreational retailers participated in the NBC News survey. The 18 retailers shared the first 27 days of their tax data because they say they believe it will help their image.

In the first month of operation, sellers of recreational marijuana are doing brisk business in Colorado. One seller said she averages about $20,000 a day in sales.

In several cases, some of those sharing data had only sold recreational pot for four days due to complications with obtaining their state and local licenses.

In a back-of-the-napkin calculation, those who shared the data say they figure February’s tax collections in Colorado likely will exceed a quarter of a million dollars a day, putting it on pace to near $100 million annually.

Read more: Pot buyers add more than $1M to Colorado tax coffers | NBC News