DENVER -- Marijuana shoppers in Colorado took advantage of a one-time tax holiday Wednesday by loading up on weed without paying an extra 10 per cent sales tax.

But those savings -- about $20 on a midgrade ounce of pot -- paled in comparison to what pot retailers were saving.

The quirk in state law that triggered the tax holiday also required Colorado to suspend excise taxes on wholesale pot. That equated to savings of $300 a pound for savvy retailers who loaded up on inventory.

"I probably saved $45,000 before lunch," said a smiling Tim Cullen, owner of the Colorado Harvest Co. chain of marijuana dispensaries.

Looking over a small tangle of pot shoppers in his suburban Denver shop, Cullen said the crowds weren't huge but the tax break would be a big win anyway.

"This is just gravy," Cullen said about the shoppers.

The odd tax waiver was triggered almost two years ago, when Colorado voters approved two taxes on recreational marijuana -- a 10 per cent sales tax for shoppers and a 15 per cent excise tax for wholesale growers.

Ahead of that vote, state tax analysts miscalculated overall state revenues for 2014. The error triggered a mandatory suspension of the new taxes.

Lawmakers decided to waive the taxes only for a single day, though voters will have to return to polls in November to authorize the state to keep some $50 million in pot taxes collected in 2014.

Confused? So were many shoppers Wednesday -- but they loaded up on lower-cost weed anyway.

"I'm just going to buy a little more than I normally do and hold onto it," said 41-year-old shopper Tim Persoff.

Some out-of-state visitors were shocked to see the virtually tax-free sale of weed. (It was still subject to local taxes and Colorado's basic 2.9 per cent sales tax.)

"I saw online there was some kind of loophole on the taxes, so I had to come buy some," said David Illig of Onawa, Iowa, who was passing through on a drive to California.

Colorado tracks marijuana sales but doesn't make the data public, making it impossible to know if Wednesday set a single-day sales record. Several retailers said the day was akin to a busy holiday weekend.

Still, shoppers and marijuana industry workers lauded the tax holiday as a needed break.

In a statewide tally made final Tuesday, Colorado reported that it collected much more in marijuana-specific taxes last fiscal year than alcohol-specific taxes.

"The cannabis community has brought so much money to the state of Colorado, this is only fair," said Chad Drew, sales manager at Colorado Harvest Co.