Your pricing actually seems just a little bit above retail, so it may be high. However, you don't have any items or budget shown for installed cabling, wall plates, beltpack cables and so on.
You mentioned wanting to expand the system and perhaps add wireless. Rather than looking at it as adding it later you might want to plan for that expansion in what you do now and then just pull the directly related pieces out, that way you know there is a path for that expansion in the future.
Connectivity can be something to address now. You are showing two single
channel and a single two channel beltpacks but would the connectivity actually be just three matching wall plates or might you have multiple one and two channel wall plates in different locations? For the single channel beltpacks, would you have single channel plates or two channel plates with a switch? Would the two channel connections be two single channel connections on a plate with a Y
adapter cable or a 6 pin two channel connection? So figuring out how many actual connections you want, what they are and where they are located is important to defining the overall system.
I personally prefer to homerun all the lines to a terminal strip, it makes the system easier to troubleshoot and allows you to readily reconfigure the connectivity. However, this is typically more expensive than daisy-chaining.
Also consider any related conduit and
raceway requirements. Surface run cable may not be the best idea in some areas and other areas may require that plenum cable be used. You could have some significant costs involved if you have to add conduit and raceway in some existing facilities.