As I tried to explain, the equal billing for all activities is the only way that makes sense. Think of it this way - if you are on a phone call with a client for an hour, you can’t be sketching for another client. If you bill 50E/hr for a call and 100E/hr for sketching, would you ever take a call? Put this way, the client should understand. Time is time. Lawyers work the same way, as does the guy coming to fix your washing machine. It’s a set hourly rate, no matter if they are just talking, looking, or doing.
As for the rate, 200E/hr was just an example. I have no idea what experience level you are at or the industry/country which will make a difference in rate. 500E/day seems very low though, IMHO.
IAB’s example rates seem in the right ballpark, maybe a bit high. Then again, keep in mind rate is only as relevant as how long the job takes or how quick you are at doing it. Also keep in mind how much of your available time the job make take up and/or what other work you do/might/can have. If you are freelance you bill a higher rate as you aren’t working 40h/week every week, so it has to average out during the slow times to net your annual take home. You also have to pay for own overhead, equipment, insurance, etc.
R