Warmoth is expensive, and i hate to sound like a fanboy but they are well worth it for a dream bass type build, Allparts are about the same but with less choice. USACG are another american custom guitar parts maker, or musikraft. In the UK Simms make parts, or some luthier will but the price is never less than importing one from american when you include finishing. Mighty mite are quite cheap and not bad quality but then neither are the Fender necks and bodies that are sold by thestratosphere on ebay. I've bought lots of parts from them and not had a problem.