You have our full sympathy here! We spent a lot of time trawling the web for a burr coffee grinder that won't break the bank. We have recently acquired a Krups burr grinder from John Lewis for £40, and are in the process of testing its durability. It is of relatively light construction, but we feel it is priced fairly, and have high hopes that it will be suitable for vigorous domestic use.
Any grinder will jam if you try to set a finer grind (i.e. bring the burr heads closer together) when it is not switched on! I have a Mazzer grinder at home, the same model that you will see in many cafes and restaurants and it is a great grinder that I would recommend to anyone if price is no hindrance. The point is that I can easily jam it solid if I try and adjust the grind finer setting when it is switched off.