Rest assured, the vast majority of the cost goes to Shapeways, and not to me, the designer, for these parts WHICH ARE CUSTOM PRODUCED TO ORDER USING ADVANCED PROTOTYPING PROCESS. I make my designs available to others to help them out, since no one else offers them through more affordable processes that involve hard tooling.
Regarding size: I can assure you that the parts are correct to the stated scale; did you order the correct scale? Perhaps you ordered 1:24 parts instead of 1:20? The scale must be selected at time of order. If you did order 1:20, please let me know what appears to be too small.