To answer the original question about Landfill - not Brownfield, they can cost more but then again, it depends on how creative you are. Some, like Harborside are costly - but then again that inclused the cost of actually capping the landfill as part of the construction cost where others make use of previously capped landfills. So it's hard to get apples to apples. That said, irrigation needs to be practically wall-to-wall. Top Soils tend to be substandard if they exist at all. Forrest may have it a bit easier out i the southwest where you can get bermuda to grow on just about anything. Getting some type of Top Soil (or sand) if none exists is the biggest hurdle. An irrigation resevoir is also another hurdle. Fill dirt may actually, depending on the location be a source of off-setting revenue. USGA greens would be a big No-No, so greens construction is cheaper. Hard surface cart path is also problematic due to the shifting subsurface. Irrigation has to be some sort of extremely strong or flexible pipe with intregral joints/connections. Fuel storage, maintenance buildings and clubhouses are also problematic. They can be located on the landfill but not utilizing normal building techniques. All earthwork is fill only, no cut. So about 3x's the normal fill is required. Also how that fillis placed and where will affect the underlying cap and hence cause future drainage problems that can't be just "piped away". Add to that, if a methane collection system with it's associated network of gas wells and connecting piping are present, these have to be incorportated into the design as improperly placed fill can have disastorous effects on the systems functionality
Other than that, construction is pretty much the same as any terrafirma course.
PS. Every landfill is created differently, so what works on one may have no bearing on another.
As far as costs, I just finished a 9-hole and double-ended range, public course under a union contract for a little over $2 million. Rough grading, and topsoil provided by the municipality. - This is just GC, no clubhouse, maintenance building, etc.