There are some Comp racers that spend more money to field a competitive car than Alky racers. Heck, there are some that spend more than some low budget fuel teams.
Comp Eliminator is my favorite class of drag racing due to the reasons stated in that very well written article - the diversity of the cars involved and the innovation found in those cars, and there is no break-out rule in affect. In most sportsman classes, performance can be bought off the shelf, at a price, available to everyone. In Comp, I would say there are more one-off custom built or manufactured engine, chassis and body parts than in any other class of drag racing, Pro or Sportsman.
Comp racers are a rare breed. They spend boatloads of money to race competitively with almost no hope of recovering more than a fraction of their investments. That can be said of most classes in this sport, but sponsorship monies that make up for at least part of the discrepancies between racing costs and potential winnings just aren't available, and pretty much never have been. These guys and girls race because they love racing and they love competition. It certainly isn't because they love money! There are Sportsman racers in other classes that can be successful enough to race for a living, albeit not many of them, but their costs for competitive performance are significantly lower than those for Comp.
As to the lower car counts, it is money, period. In this economy, everybody is getting pinched in one way or another.