Too many people seem to look at audio and AV systems as "equipment" they purchase rather than as solutions to help effectively serve their goals and vision. And it is way too common to find churches trying to purchase new audio systems without having any good idea of why they are doing so, what their expectations are for those systems or how they plan to implement them, they seem to believe that simply implementing new technology will inherently result in an improvement and there are plenty of vendors more than willing to support that perspective.
Thus I am a firm advocate of starting any discussion of church audio with first discussing the situation and goals as those should be what drive any actual equipment or technology decisions.
This may be particularly noticeable in the HOW market, but it is common across all markets. The first thing to discuss is the goal, till then there is no way to define a solution.
Too often a solution is implemented as a black box (little sound go in, big sound come out) without the end user having an understanding of how to use it. Anyone can drive a race car, only certain people can drive it fast.
Any proposed solution, in addition to the equipment, must also consider operation and maintenance. The operation aspect of that solution will require that the end user understand how it works and be able to use it as designed. Often that means you'll need a trained operator, either through formal education or self-study. That represents an expense that's often overlooked.
If a church board budgets a large sum to purchase audio equipment and installation services, has it also budgeted proper training in live audio production beyond the sales reps' "here's how you turn it on" seminar? If not, dissatisfaction will likely occur.
If the church has their staff (either paid or volunteer) properly trained prior to purchasing new equipment, they may find that the performance and usability of the existing stuff improves, and the staff will be better equipped to determine the best solution forward and use any new equipment to the greatest advantage. As time and technology progress, "professional development" training will be necessary.
There's also the need to budget for maintenance, from regular service of equipment to replacement of failed parts. That's another thing that often ends up being reactive rather than proactive. You end up wondering where the money went rather than telling it where to go. When budgeting for a new system, the maintenance budget will also likely need to be replaced.