Depends how much work you want to to do yourself.
When I changed from webered Xfow to injected zetec 10 years ago I did all the work myself including making various bits & bobs - engine mounts, rear exit exhaust, Alternator bracket, inlet manifold, etc etc.
my costs are below though I'm sure many of thse have come down in price since I converted mine.
Used guaranteed Engine £250 - now they're about £100 from local breaker - so I have 2 spares just in case!
TB's Lotus Esprit £50 [NEW from Lotus parts fair], some of my mates use bike TB's they're £100-200 a set maybe less if you're lucky on Ebay.
Emerald Ecu £520 And rolling road set up at emerald £250
Sump £150 [Retro frod]
Flywheel £20 I machined & modded it myself
4 branch Ex Man'f - [Westfield] £250
Clutch £70 [Sierra DOHC]
Crank Spigot bush £10
Remote oil filter housing and blanking plate £60ish [Burtons]
Waterail £180 [Retro Ford]
Water Hoses £10 I bought a job lot at autojumble and made up what I needed.
Fuel rail and injectors - Standard K series fit straight on

£10 from local breakers
HP Fuel pump [Sierra in tank] £10 from autojumble
Starter motor [Sierra] from car I was breaking
Because my car originally had a Dynamo I converted it to alternator [Sierra]
Various senders - Throttle position, Flywheel, lambda etc I got from a Sierra that I was breaking at the time
It really does transform the car, mines a standard engine and gives ~160BHP and always 30+MPG, with smooth running easy starting and gutsy performance, Oh almost forgot I don't leak oil either so I can now paint the garage floor, which the wife likes

I prefer the silvertop cam cover - Looks very similar to Lotus TC cover.
I bought a pipercross airfilter but have never bothered fitting it the Rampipes make the TB's look like the webers used to

Hope this helps
Of course you can sell all the bits you replace, eg. my webered X flow would now make £1K plus on ebay were I to sell it, so you can recover a lot of costs if feel inclined, Me because my cars a Lotus7 I kept all my original bits So I can return the car to original L7 spec If I ever wanted to.