What are the arguments in favor of developing the needed systems internally?

It is late Friday afternoon, and Kyle Baxter, president of Baxter Manufacturing Company, Inc., and his sister, Sue Barkley, vice president for customer relations, are discussing whether or not to purchase the Effective Management Systems manufacturing software package proposed by manufacturing Vice President Lucas Moore.
“I’m really fearful of buying such a large, complex software package given our past experience,” Baxter exclaims. “What do you think?”
“I really don’t know,” Barkley replies. “We do need manufacturing software, and there are some obvious advantages to purchasing this software. We have had bad experiences in past attempts to buy such software, but we have learned from some of our mistakes, so we might be successful this time. But I have been impressed by the success that MIS has had in building new systems for us, so I am in a quandary right now.”