You're basically renting someone else's "home" - even though they themselves share it with other people. So think of it that way and I think it makes it easier to understand.
You can deal directly with the "home" owner -- there's a sub board here on Disboards, under the Disney Vacation Club board, that is specifically for renting. Be sure to check out the stickies at the top where they talk about contracts and rules, etc.
You can deal with a middleman, like David's, who will then talk directly with the "home" owner. It's up to you.
My understanding is that there is going to be a subset of "owners" who, for whatever reason, don't want to stay in their "home" at the time you want to go. Some of them will be amenable to dealing with you directly; some of them will go through David's to help them; and some of them will ultimately just let those points expire. I doubt there's much overlap between the categories, so you might want to investigate both the board here on Disboards and contact a broker like David's to see where your best opportunities are.
As far as the price, no, generally the price you'll pay is far less than rack rates for the room. Which is a big reason there's a market for renting
DVC points. I'm not sure what the going rate is -- again, a perusal of the rent/trade board here on Disboards as well as a quick scan of a site such as David's will give you an idea of prices. Be aware that DVC has several qualifiers that affect the price (in points) of a room -- there are about 5 different seasons throughout the year, the size of the room will change the cost, the view of the room (parking lot, theme park, pool, etc.) is reflected in the cost, the actual resort you want, and the days of the week you stay (Friday and Saturday nights cost more than the other days of the week) are all factors to consider when trying to compare costs. So if you see a listing for "$9 a point" from one person and "$150 a night" from another person, you'd need to know if they were for the same resort, size room, time of year, view, and days of the week to see how they compared. Even if you're told that both are 15 points a night, that might be because one is a studio while the other is a one-bedroom, or one is during Christmas while the other is in January, etc. So, when you start comparing, keep in mind resort, dates, room size, days of week, and view.