Even as a beginner I think you should be charging more. Hardly surprising that people are taking you for a ride if you're charging so little, they're not taking you seriously. Remember that out of that 100 euro you have to pay tax and you're supposed to be making enough to get by as well, but on top of that as a freelancer you have to pay your accountant (unless you can do you own books), Health Insurance, Rent (office and/or home), Buy software + hardware etc etc ... all things that employees take for granted but you have to fork out for yourself.
I don't really agree with Dropbop above, Designing a front page takes most of the design time, adding more pages is the quick bit.
If you get a client on a really tight budget then I'd show them a pre-made template and let them choose one of them, then you can really turn a project around quickly, but you still have to charge for the time it takes to deal with the client (calls-emails), look for a suitable template, sometimes those templates are a bit of a dogs dinner and you'll have to rebuild them etc etc ...