Money -- part two

I'm confused. Spain is a strange country. The first time I went to the hairdresser I paid more than 100 Euros. The first time I went to the doctor I paid 70 Euros. The pay road (AP7) costs 6,10 Euros. BUT...

When I went to the hairdresser yesterday they only charged me 21 Euros. When I went to the doctor on Monday to check the deep cut in my smashed toe (au au au!) it only costed 20 Euros! I usually pay with my credit card when I drive on the pay road. It turns out that they've only charged me 5,79 Euros the last few times I've passed. I know my understanding of money is below average, but this really doesn't make sense! Can someone explain this for me? :)

On a different note: Have had a lovely Easter with my friend R. and my sister, her husband, and Oda and Sivert. Pictures and an update will come soon.