The money question is always a personal one. A scout shared his experience which is that they get such a wide variety of reactions to $'s and it comes down to where the prospects is from, cost of living in the area and their personal life style. A $200,000 signing bonus he said is looked at so differently by a family living in a major city in CA or NY as an example than it does by a family living in say OK/MO. Same dollars, just different perspective on its value. I think it really comes down to how badly the player wants MLB as a career and whether they are mature enough NOW, out of HS, for this career or not.
I agree with NVR1, you need a plan for the minor league lifestyle. How will the player manage on the pay provided to them during the season. What sources will they have to supplement their income if needed, either by a signing bonus, family support or can they fit in a job in the off season while they condition. Its a personal decision. For me, out side of the very top players, if it takes "set for life money" than I would wonder about how badly the prospect really wants a career in major league baseball. But then, that's why the decision is so personal, with no one answer for everyone.