This is what I have found quite usable approach. When the sales person has been explaining for some time how difficult it is to estimete the price, I simply ask

This is what I have found quite usable approach. When the sales person has been explaining for some time how difficult it is to estimete the price, I simply ask how many zeroes he thinks the budget is going to have. This more often than not results to answer like "oh, I would think it is between 60k and 80k. It seems that most salespeople are not able to sense the difference between asking for indicative quote and trying to figure out orders of magnitudes in costs.