Vicente didn't want to tell Lukas the whole truth right away. That would be compromising and unnecessary. However, he did want Lukas and some other professionals on his side.
The cost would be high, as Lukas imagined. But the benefit would be much greater.
For example, by having an alchemist on his side, Vicente's family could raise someone who would be committed to serving the family and who could produce exactly the pills and potions they needed.
Though the cost of maintaining such a single professional would be high, the return and potential they could provide were immense.
Vicente would have to spend a lot of money to have each of these professionals on his side. But each of them would accelerate the rate of progress of his group relative to its numbers and capabilities.