If you go to your blogger Layout, click 'Edit HTML' and tick the checkbox where it says 'Expand Widget' you can view the xml file for your page. Just scrole down a little bit and you will see some css. Some of it is imported but you can just edit that. So, even though it is inside of xml, it is still plain and simple css.
Go further down and it gets more tricky, but if you study it logically, it is also just html wrapped in xml. The only reason it looks funny is that there are a number of options.
So, to answer your question, it isn't a matter of payment, it is a matter of the template reader. If you created a static HTML page, you couldn't modify it in as many different ways, from outside the code, as what you can with blogger.
I went through the struggle of trying to carefully modify the html without destroying my site when I first started using blogger. Then I did one simple thing...I created a dummy blog, one that I could just play with without fear of what I would do to my own site. If you try things...say put a peace of text in here and there, or change a color of a section, then soon you start to understand how your xml gets sowed together by blogger's xml parser...what you can modify so that it still makes sense.
Try commenting out sections, using normal html comments and see how that goes.
Let my try to explain it like this. This is not how it works, but basically just how an xml template might work in general:
<b:header>Here is where whatever header you select gets put in</b:header>
<b:main>Main post in here</b:main>
<b:comments>...
<b:sidebar>....
<b:footer>....
Then you can go and change it in blogger's nice interface, or even with the many api tools if you really get clever. Then each time your page is called up, blogger has a parser that runs through, and looks at each section, and sticks whatever you selected to be in each peace of html, and puts in in the page.
But if you go and stick some html strait inside of that xml, it is stupid (sort of) and just sticks that right into your page. For example, at one time I had ads under my header. The code for the ad widget was just put into the page and worked brilliantly.
So you still have plenty of room for editing it even if you only understand the html and css.
