Not as bad as when Atlus international (also known as Medsea and had other associated names/companies) charged 20% commissions, right under the nose of the government, who were too busy looking the other way.
I took a job working for an estate agent when I came to Spain, purely to understand how the market (and estate agents/developers work). It absolutely disgusted me, or the company I worked with for starters - Spanish homes just for you. Utterly immoral.
I was asked to sell a property to an elderly gentleman, who had an advanced illness, only a few years to live. On his 'wish list' was a quiet apartment, with mountain views. I knew exactly what we / agent - had in stock & knew the perfect apartment. Took the client there, he was happy - job done, or so I thought.
Went back to see my boss - who tells me 'you can't sell him that apartment' - I say 'why'? He says 'because you need to sell him a different one nearby' - WHICH WE EARN MORE COMMISSION ON. I say 'those apartments you suggest back on to nightclubs, noisy & exactly what the client does not want', he didn't care - I wouldn't comply as thought it was disgusting and greedy behaviour.
I next tried to fight the case with a developer of a client who had been promised a garage on a new build, they'd fudged the paperwork and basically the client, was not going to get his garage, that he'd thought paid for. I stood toe to toe with the developer, telling them they could not behave this way - the answer 'what do you care, you have your commission'? Well that may have been true (or would have been if the crook had paid me), but that's not the point, I also thought I was there to help 'my clients'.
After a year of this farce and studying the Spanish property market, I decided to bail & simply could not abide the type of people, no crooks, I had to deal with.
I'm sure there are some decent and honest agents out there - the problem is, no one qualifies you in this, there's little recompense if you have been misled and worst of all the lawyers in Spain, many are of not great. I've seen so many errors from a long list of lawyers, I wouldn't know where to begin - the first thing is to check everything, ask every question and do so in writing. Or better still take the advice of someone you know who has lived in Spain for a while, who has no hidden agenda ;-)