How much should a small business pay a marketing agency?

In West Yorkshire, most small businesses working with an independent agency pay a monthly retainer between £800 and £4,000, with £1,500 to £2,500 the most common band. Below about £800 a month it is difficult for an agency to allocate enough senior time for the work to move anything. Project work is priced separately: a small business website typically runs £3,000 to £12,000 and a brand identity £2,500 to £15,000.