GLOBAL AUTO MAKERS are nishing to challenge the dominance of Toyota Motor Corp.'s Prius hybrid with a slew of eco-friendly vehicles. But Honda Motor Co. is likely to pose the most formidable threat to Toyota when it unveils its new Insight hybrid car Thursday at the Paris Auto Show. Honda is betting that the five-passenger hatchback, set to go on sale next spring, will steal away Prius buyers by delivering greenness for fewer greenbacks. Honda has yet to disclose precise details about the car or its cost, and it calls the car to be shown in Paris a concept, but it says Insight "will be priced significantly lower than hybrids available today." Analysts expect the model will cost under $20,000, undercutting the current $22,000 starting price of the Prius. "It will be the first affordable hybrid for everyone," says Tatsuo Yoshida, an analyst for UBS Securi