Booking.com Perl Developer – Amsterdam Full Time interview questions

I was contacted by a recruiter from England, and was told that she was very impressed with my LinkedIn profile and asked if I was interested in a position in Perl programming. I said yes, so two days later I was interviewed by her boss. Very nice people, we had a 15 minute conversation through Skype about my experience and skills, and he gave me details about the job. The company was Booking.com, the position was in Amsterdam, etc., and he sent me pdfs with details and links to YouTube videos about working in Booking.com. However, the salary of 45.000 - 60.000 euros gross seemed to be low for my 18 years of experience in the web industry and Perl programming, so I asked if the amount was negotiable. He said that Booking.com usually offers between 50.000 and 55.000 euros plus bonuses for that position and that there was a 30% ruling for foreign nationals. I thought about it for a couple of days, and agreed to go ahead with the application process. About a week later, the recruiter contacted me again, and told me that Booking.com reviewed my application, and found that my experience looked good, but decided not to move forward because they wanted a bit more depth and that they preferred people who have worked for large companies (I'm self employed and have never worked as an employee).