The real trade being made
The choice is not between an expensive model and a cheap one. It is between paying for control and paying for reach. Direct selling keeps the margin, the customer relationship and the market feedback in your hands, and you pay for it in hiring, ramp time, travel and management attention. Channel selling buys you presence in places and segments you could not economically staff, and you pay for it in margin and in distance from the end customer.
That distance is the part most often underestimated. A partner led business hears about customer problems late, hears about competitor moves not at all, and cannot easily test a new pitch. For a mature product in a defined market that is an acceptable price. For a product still finding its shape it is close to fatal, which is why the sequence for most companies is direct first, channel once the sale is repeatable.