"...and after all these years of my paying her 3 shillings a week, too!" That does give me a rueful smile ^^"

You can see why CAM offering the equivalent of 10 years' wages for a few letters would look very tempting to impoverished, overworked maids. Absolutely. The "treacherous valets or maids" can't all have been disgruntled employees or simply bad'uns. They were just poor people being taken advantage of - by Milverton and their employers.