Thats how it was with my estate agents when I sold. Its a bit of a con really, as rather than charge say 1%, they worked out that 1% of their "valuation" of my house of £200k is £2000 and so thats what they would charge for their fees as a fixed price. So you agree to that. Then of course, it transpires that they have overvalued your house and you end up selling for £180k and the estate still gets his £2k which works out at a higher percentage of £180k.
Mine has a cracking set of pins and wears short skirts and high heels whenever I've seen her, so I figure I also get my money's worth that way