I think it really depends on what you want it to be capable of. The system we have here in our building covers a decent amount of area, runs more or less over coaxial and a couple of fiber runs for the really far places, and is standalone in regards to recording and storage. The video is kept on three different recorders and uses a single unit to view them over the network or through regular CC monitors. It also was about $25k, for the equipment alone. It can also convert the video into different formats like WMA and quicktime, and if we wanted, we could hook it up to our gateway and broadcast all of the feeds over the web. The capacity on it is about 4,000 hours of recordings and you can mark each day's or hours as to sore or allow to automatically record over. It saves the video from each camera as it's own files named by the camera and the date.
The first thing that I would suggest is to determine how much square footage you want to cover. The next is the conditions (indoor outdoor, poor lighting). Then after that how much you want to buy upfront (the 25k mark was spent over two years in three installments, so I am sure if we plopped it down all at once, we might have been able to bargain a little with the vendor) and how much capacity you want. Then after that, factor in how easily it would be to add more cameras, not just as hookups to the recorders, but also the costs of adding new runs and new cameras.
We had decided on the plans and then had them run the wires all at the same time, even if the line ran to nothing, but would eventually have a camera. Good electricians and cable guys can be alsmost as expesinve as the actual hardware. In some places, that did not have power to run the camera, we needed to run new conduit to get power in that spot. There were some Power over Line solutions, but they were either too expensive or did not perform the way we would want. It might be different now. If you do not have any special electrical requirements, I would do the cable pulling yourself, or when you hire a vendor, your your in house labor to assist them. Much of that kind of work was really basic and they had what looked like high school students doing the coax pulling, while 1 grey haried guy was doing the electrical.
We also had asked the local PD what they used, and went with the same vendor, but not the same system.