I am assuming you know this, but maybe you don't: 1-2 Smithies with no Villages is usually a better strategy in the Base game than Smithies and Villages.
No I didn't know that - thanks for pointing it out. But if smithy/village is too slow, surely lab chains are even slower (since it's quite a bit harder to get $5)? So wouldn't a couple of smithies be better than labs? And if that is so, why make labs cost $5?
Please understand, I'm not saying the prices are wrong, I'm just asking the questions since I knew you would all know more about this than me.
Two (related) reasons why Lab chains are better:
(1) One Lab by itself in your hand has a better chance of drawing the next engine component than either Village (which draws half as many cards) or Smithy (which will draw engine components dead).
(2) One Lab by itself adds value to your hand, even if you don't draw any other engine component. A Village by itself just replaces itself in your hand and provides no actual value. A Smithy by itself is better, but if it draws other Villages or Smithies dead, it's actually worse than not having played it at all -- because not only didn't you get anything good out of playing the Smithy, but you skipped over the engine components you would have gotten next turn.
If you manage to fire either engine, you're probably fine, as you'll draw a lot of your deck and thus presumably have money to spend. But you rarely if ever want to pursue a "pure" strategy of one or the other. They'd usually be components of something more complex. At the very least, a Lab chain should have a key terminal in there that you can end the chain on. That could be any number of things. To pick a random example out of a hat, say you've got one Militia in your Lab deck. Having it at the end of a Lab chain means you'd get to play that Militia almost every turn, thereby hopefully shutting down your opponent. You could play a Militia every turn by buying out the Militia pile too, but a deck full of Militias won't buy Provinces, because instead of drawing all the Treasure in your deck (as a Lab chain would), your hand is clogged up with a bunch of Militias, only one of which you can play.
As was mentioned, "pure" Village/Smithy engines are actually outperformed by a simple money deck with 1-2 Smithies thrown in. Still, the
principle of constructing a Village/Smithy engine is important to know, because if you are (1) able to swap the components out for stronger variations, e.g., Torturer instead of Smithy; or (2) able to integrate other strong action cards into the mix, you can build some pretty brutal machines.
And you can blend two kinds of engines together, too. For example, Villages can be added seamlessly into a Lab chain if you'd like to use said Lab chain to spam
multiple terminals every turn. Additionally, adding a couple Labs to a Minion chain (caution: don't do this until the Minion pile is depleted) may mean that you are able to play a higher percentage of your Minions for money rather than for cycling.
I do see where you're coming from. When I first started playing Dominion, Laboratory's $5 price tag was truly perplexing. And as I didn't yet realize just how solidly and carefully the game was designed, I didn't trust that the price was correct. But once I started using it and getting a feel for how it plays, I realized why it's a $5 card. Frankly, since all you've got so far are Base and Intrigue, it's actually one of the
strongest non-attack $5 cards, weirdly enough. Some of the later expansions have stronger alternatives to Laboratory, as well as additional strategies that obviate the need for them. But even now there are still a lot of kingdoms where Lab is amazing.
But...
So wouldn't a couple of smithies be better than labs?
If all you're doing is buying money plus either a couple of Smithies or a couple of Labs, then you're right, absolutely a couple of Smithies is better. It all depends on what you're doing, though. If you have a Witch in your hand, Smithies don't help you play it more often.