Is Lookout usually a good pick with a Big Money strategy?
I certainly agree. For the hand playing it, Lookout is a dead card. Since you're considering a Big Money (BM) strategy, the natural comparison is against Silver. The first time you play it, if you're lucky, you remove a single dead card from your deck (an Estate), you're back to where you started, and you had to play with a 4-card hand that, had you had a Silver instead, could likely have bought you a good $5 or Gold! By the time you've played the Lookout twice, it's probably turn 6-8; the game is close to half over. The Silver could have catapulted you to Gold or a good $5 twice now, and you'd have a Silver in your deck too.

Lookout is fine if the BM is flavored by Cursing, and Sea Hag in particular. In this case it removes negative points, hits more dead cards, and has a longer time to work in the more drawn-out cursing environment.

I would be very surprised if Lookout/Smithy/BM beats Smithy/BM, for the same reasons as above (and because the Smithy can draw the Lookout dead!) For Lookout to be good in the absence of Curses, you need to have an engine in mind.