Visual Studio has a large installed developer base. The cost of a modification is directly proportionate to the amount of code that a programmer must decipher and then write. Object-oriented dictates a design that stresses localized changes. 2001 was developed using an object-oriented framework. Since there is a high degree of code reuse changes are localized in one area.
Complex modifications are relatively straightforward and easier to estimate.
Reasonably priced Many of the popular Windows packages are priced so that they exclude a large portion of smaller growing businesses, and the smaller business market is the highest growth area.