We pay about $0.30 per 1,000 gallons in electricity or 0.03 pennies per gallon*. If electricity was 100 times more expensive that would still only be 3 pennies a gallon. I would not expect to use more than a gallon per minute to keep the laser cool - much less I think. That puts my water cost at about 15 cents for a full day.
*1,200W well pump. Two hours to pump 1,000 gallons (1,000 / 9 gal per minute = 111 minutes) uses 2.4 KW hours. At $0.12 per KWH that is 28.8 cents per 1,000 gallons.