The key to answering this question is to recognize the impact of a guild-like structure on competition. The correct answer is B because the restrictive nature of the profession prevents competition, which would otherwise drive down costs. Option A is incorrect because while training costs can be high, they are not the primary reason for high overall costs. Option C is incorrect because high demand without restrictiveness would not necessarily lead to high costs. Option D is incorrect because a guild-like structure typically resists change and innovation.