Hummel figurines are manufactured under strict conditions, yet even the factory cannot prevent the occasional piece with crazing or cracking of the glaze, reaching the market place. And, as well, crazing can occur with age.
Damage to pieces will always be a post factory/store condition. The usual problem is a tiny piece broken off - the end of a braid, the tip of an angel's wing, etc.
Major damage is when there is complete separation of say a head, or arm or leg on a piece. In such cases the usual situation found is a rather amaturish repair, easily noted upon examination. A professional repair may be near impossible to note, however; due to the cost of professional work, such repairs are rare as they would usually exceed the value of the piece.
Attempting to price a Hummel, or any other quality porcelain piece that has some form of damage is difficult. It is enough to state the price will be drastically lower for any major damage, even if repaired. For even minor damage there should be either an "open end" (no reserve) or minimal reserve on a piece and the price should be substandially below other like pieces being offered at that time on eBay.
For crazing on the base or under the piece, the amount of price reduction expected will relate to the location and amount of the crazing. And where the crazing occurs on areas of the figurine, the expected price reduction should reflect the specific areas impacted. If on the face, major reduction, dresses or areas of closthing far less reduction.
Good luck and beware - always beware.