A very late answer, but I hope it's interesting to you. Your question should probably have been redirected to the Short Answers thread, because it's not one I can give a really in-depth answer to. Servants during this period were paid in cash, or in a combination of cash and board, and the cash came on either a quarterly or, sometimes, annual basis. The 1881 edition of Cassell's Household Guide was fairly explicit:

It is customary in this country to hire domestic servants by the year, in which case the wages are paid quarterly. ... It is the duty of an employer to pay his servant the wages agreed upon, and to house and to feed him in a suitable manner.

In some cases, paydays seem to have been tied to the quarter-days: March 25, June 24, September 29, December 25. It had been long-standing tradition for these holidays to provide a framework for wages, rents, academic terms, etc. but by the end of the nineteenth century, in urban or suburban contexts, they weren't as relevant as they had been.

Cassell's (1881) recommended twelve to fourteen pounds per year for a "general servant" - basically, a female servant who did the cleaning and cooking, usually employed in a household that couldn't afford a cook as well as a housemaid, let alone a lady's maid; Life Below Stairs: True Lives of Edwardian Servants suggests that the average wage for a housemaid in 1899 was about sixteen pounds, while Charles Booth's 1896 Life and Labour of the People in London gave fifteen pounds, eight shillings as the average wage for a single servant working alone for one family - but, and this is the important part for your question, he also noted that the actual wage tended to be higher among richer households in the West End, and that newspaper advertisements for servants tended to list lower-than-average wages, because the wealthy didn't need to advertise. On the whole, he noted that the average wage per servant rose as a family employed more.

Kitchenmaids and similar positions doing dirty work or particularly behind-the-scenes tasks (like the hall boy or hall girl, essentially servants to the servants) earned the least, while those with specialized knowledge, like the cook or lady's maid, earned the most. This affects the average - a family employing a maid and a cook might pay the maid the same amount a family only employing a maid would, while still turning up a higher average - but as mentioned above, the base rates were better in wealthier households even so.