Although delivery is a legitimate cost, be cautious. Determining delivery charges to a client is sometimes not a matter of cost but rather the desire for additional profit margin. Try to negotiate. For that matter, don't forget to reserve them for the evening if that is when you're forced to accept delivery. An exceptionally long delivery is subject to additional charges from the dealer.
Installation is the most common way to far exceed a project's estimated budget.
If possible, installation should never be performed on overtime. If your building allows you to use non-union labor, inform your dealer. Non-union labor can significantly reduce the cost of union installations. Try to have an office handyman, or building maintenance man put together small items like bookcases, or doors on cabinets, bases on tables etc. Experienced installers should always install systems.