As andyb noted above, the principal reason for a draft - and this is true of the Rule 4 (June) draft as well - is to drive costs down to less than would be the costs in a truly free market.
If you drive down the total amount of money that flows from MLB to the Dominican Republic (and other Latin American nations), the result will be that you get less talent out. It's not like the United States, where high schools, colleges, families can just foot the bill for young player development.
So...if a draft undercuts the current economic arrangements in Latin America, to "save money," then unless MLB creates other channels to pump that money back into Latin America (which as was noted above, isn't likely to happen), the result will be less Latin talent in the major leagues.
To put things more simply... you get what you pay for.
Personally, I think I might find it amusing to watch the MLB cartel shoot itself in the foot. I don't like monopolists. (Although it wouldn't be very "amusing" to see more latin kids cut off from the opportunity that baseball provides...) The pathetic part of all this is that, in terms of MLB's total revenue, it's not a lot of money; it's more a case of sticking it to the young kids, the amateurs, for relatively minimal savings...just because they can, or perhaps because they have some non-economic reason for not wanting to pay market rates to these kids.