Does 多 always come after the measure word？
多 is used for approximate number, which is one-tenth of the measure unit prior to 多.

四块多美金 means 4.0-4.9 dollars. 四多块美金 is not correct, 多 should be placed after the measure word 块 for unit digit.

三十多条蛇 means 30-39 snakes, and 三十条多蛇 is not correct, because the measure unit of 蛇 could not be decimal.