If it were simply a money saving issue we would all be carrying Hi-Point Pistols.
Price per pistol is one reason. When I look at the rapid growth and continued dominance of the Glock in law enforcement I draw a few basic conclusions.
They are well made, funcitional, accurate and very reliable.
They are very competitive in price.
They have an excellent customer service history in the LEO community.
They were the first, and in many ways , still lead in the polycarb pistol family.
Smith and Wesson came to the table very late in the polycarb pistol game, as a result they have paid a price for that. By the way I currently carry a 5906 on duty. In March I will be issued a Glock 17. My department (110 officers) went through a 2 month "Test and Evaluation" that included the Glock 17/19. S&W M&P9, and SIG 229. Every officer shot all three and gave their input. The rank and file voted and the Glock won by over 90% margin.