But they're there. One way to ensure consistency and integrity across projects is to make one person or a close-knit team the visionary of your architecture. Most developers will fight you on this. They're focused on delivering their piece of the system, and might not understand how their piece could be leveraged on other objects. The result can be a fragmented architecture.
Consistency demands that all developers agree to build systems the same way.
This includes designs, coding styles, standards, and documentation. When all developers agree to do this, the savings can be substantial. Any developer can pick up another's code and immediately understand what she did. As a consequence, you'll be able to leverage developers across projects. The payoff happens a long way down the road when you're still maintaining your system.