I think those prices will be pretty hard to replicate.

I paid $1800 for my conversion + a ferw beers & dinner for Craig to help me. Mine is a Torsen Type 2 out of an NB8A
BlackRSC... paid about $1500 for his from Lou. out of a Clubman i think.
Both those were a 4.1 ratio.
It would also be advisable to have a proffessional install the crown & pinion. which should only be a few dollars if you do all the hard work of installing your own Diff when its all done. If you have someon like Mania or someone proffessional do it for you expect about 2-2.5 hrs labour. so it would be somewhere around $150-$250 to have it all done. But like slammer said If you have to pay someone to do all the bits for you......try to do it all first go.
uninstalling & reinstalling a diff is a piece of cake. Once you know how to do it

I never have enough strength to lift it back into place by myself.