Whiteline are pulling your leg though. I made a set of rear ones using four m10 rose jointed female rod ends, two m10*1.5 bolts and some graded m10 rod that i hacksawed down to size from wickes. I may hasten to add that my engineering skills are very, very basic.
You can adjust preload and they cost about £15 quid for two. The fronts are a bit more involved; i have got racing dynamics ones on the front but they are a bit costly after tax etc. No reason why you couldn't build four droplinks for under £40 quid!
The only modification you have to make is to drill the U bracket holes out to c10mm with a drill so that an m10 thread can fit through (rather than the original m-8)
Note these are for the rear, fronts are slightly more involved but same principle.