Tim is right. The actual lodgement of a caveat is a simple process. The time consuming part of the process is ensuring the lawyer has a good understanding of your facts, with proof being seen of some key facts, identifying you and then considering whether or not to apply for the caveat. If the lawyer places a caveat without a sound legal basis, then you may be taken to court and be forced to remove the caveat and pay the other party's damages and costs. You then sue the solicitor saying you should not have placed the caveat for me.
Solicitors don't like being sued because they did exactly what the client requested. Especially when damages in real estate cases can easily run over $100K very quickly, all for something that likely costs you <$1k in legal fees.