I dunno the economics of the smaller tankers, but...
For the DC-10, $26,000/hour, 12,000 gallon load, and let's say they can turn the plane around 2x an hour. That's 24,000 gallons an hour, or $1.083/gallon to deliver retardant, not including retardant costs.
Water weighs 8.34 lbs per gallon. With the retardant in it, let's say 9 lbs/gallon.
Shoot, USPS Overnight for that weight is $38, Priority Mail is over $8. That seems like a pretty good rate for spot-on delivery.
OTOH..
One story I read said that the plane could cover a half mile per drop. That's a mile of fire line an hour for $26K. Or, for an 8 hour day, 8 miles of line for $208,000.
From
http://www.fs.fed.us/fire/people/handcrews/about_handcrews.html
"The crews consist of 18 - 20 men and women ..."
"In brush a Type 1 crew should complete 6 chains in an hour..." (A chain is 66 feet.)
6 chains an hour is 396 feet. 8 hour day = 3168 feet/day/crew (I know they work longer. I'm trying to get a comparison to the jet.)
8 miles of line ( what the jet might do) = 42,240 feet. 42,240/3168 = 13.3 crews to do the same amount of line.
From
http://www.dnr.wa.gov/htdocs/rp/aviation/helitak/employment.html
A Helitack boss tops out at almost $15/hour. Let's say the whole crew averages $12/hour.
So 20 person crew x $12/hour = $240/hour wages. Benefits might add another $100/hour. Support (food, fuel, vehicles, equipment, medical) has to be at least that much again. So a crew costs at least $780/hour, or $6,240/8 hours.
To cut our 8 mile line in 8 hours takes 13.3 crews. 13.3 x 6240 = $82,992.
But, that's if every crew is on the line, ready to cut. If they have to hike in (and they will, no doubt). then they get paid for "travel time". That could double the cost to $960/hour/crew, or $165,984 for 8 miles of line in an 8 hours day.
That's within 20% of the $208,000 cost for the jet,.
I know there are still some unaccounted-for and intangible costs missing from the above calcs. And I know a retardant line isn't exactly the same as a hand crew line. I didn't include the cost of retardant. (Couldn't find any good refs in Google right away.) I'm sure Exsmokey can throw a few rocks at my back-of-the-keyboard analysis.
Still, I don't think that the numbers are too far off and that they show that the expense of the jet retardant bomber seems to be close enough to hand crews to make it a viable alternative, in situations where it's can play to its speed and capacity, and other strengths and limitations.
(And I'm at the mercy of the references and resources (including newspaper articles) being accurate. That's always risky.)