the kit i was able to use is about $500 worth of tooling for the jig, router and drill/mill bits it uses. and thats assuming you already have a 5" bench vise on hand, and some kind of corded or cordless hand drill.
but thats a buy-once-cry-once kit (other than the drill/mill bits anyway, which any knucklehead can easily damage thru mis-use) that will allow you to mill out pretty much as many lowers as you could imagine wanting to have, milled to some kind of quality that doesnt look like your dog chewed the FCG pocket out for you or you let your nephew chisel it out with a hammer.
its definitely not the kit that joe-hobby is gonna get to mill out one or two lowers, unless your intent is to do so and then re-sell it to get some $$ back out of it.
but it also comes down to the age old "how do you want your work done" conundrum
fast, right, cheap - pick any two!