The classic sales funnel model is quite accurate, but only if you expect the funnel to be seriously leaky.
People come out the bottom only if they avoid falling through the cracks before buying.
An alternative model is the inverted funnel.
In a way, it’s more accurate; each step closer to buying something is more like climbing up than sliding down.
In other words, if you don’t keep people moving up, they’re just going to slide back to the beginning and off your funnel.
But you shouldn’t ask people to climb a mountain before buying.
The most useful model—I believe—is the conversion path that consists of all the steps people take before buying.