4/20, or April 20, is the unofficial national holiday for marijuana smokers, and the University of Colorado's (CU) Boulder campus is notorious for celebrating by holding one of the biggest public smoke-outs in the country, typically attracting over 12,000 people.

CU has now revealed it spent a total $107,794 to end this year's smoke-out by closing down the campus. Perhaps even more shocking: this is about $17,000 less than last year's costs, when CU shut the campus down to the public for the first time. 

And while those taking part in the celebrations may laugh, UC administrators certainly aren't.

"While this is not money we are eager to spend, we have to ask ourselves what the costs are to us for having our work disrupted or having a student or bystander injured because we allowed the gathering on the campus," Chancellor Phil DiStefano said.

Here are the CU's itemized costs to prevent this year's 4/20 party:

• $70,850 for CU police/security/dispatcher/parking overtime and labor costs for officers from outside agencies
• $9,881 for Argus security staff assisting with police/parking operations
• $4,431 for fire department/ambulance coverage
• $12,025 on miscellaneous expenses, including equipment, supplies, operations facility rental, printing, and food and water for personnel
• $5,016 for parking equipment/rentals, such as cones, barricades and variable message signs noting the campus closure
• $5,591 for overtime labor costs in facilities management (groundskeeping, locksmiths and other facilities employees).

Since the 4/20 shutdown reduced liability and hazard claims for CU, campus insurance premium rebates covered the full cost of closing down the campus, according to university officials.