99% of all the projects I've ever done have been in gated communities. The fees cover the insurance and the added cost of the personnel for the additional "traffic" coming though the gates as well as the insurance riders for the "additional risk". Sometimes that is an expense paid to the security company and sometimes it is a cost incurred by the builder. Either way, regardless of who is the recipient, the home owner will incur the costs.

Is this cost usually discussed with the buyer BEFORE the closing? I have had houses built in the past, and I was informed of any additional fees that would incur when I signed a contract. However, this developer isn't even discussing these fees until the closing, which means the buyer does not know about these costs until it is too late.

Ask a lawyer.

Your best bet at this point is to be up front and ask your builder about them. Ask them for a list of all the fees due at closing, where the fees originate from and if or how they can be avoided. Do everything in writing. Is your builder the developer? Is the fee for using a "non-preferred" builder or are they for additional costs incurred by the community, fines for violations, inconvenience fees or the like, or is it a "just because I can" fee? Who is charging the fees and who is the recipient of the funds?

In my experience many of these hidden costs are found in the restrictive covenants or deed restrictions and don't have a set value or even a formula for calculating them but are considered legal and often fall under the blanket of "security" even if it is a task performed by others (i.e. landscape or road repair/cleaning). Even though they aren't openly discussed they are most likely mentioned, however vaguely, somewhere.

Every community is different as is every contract so you really need to ask and do your own due diligence so you know what to ask a lawyer.