I'm new to xoops, but somehow i got the impression from the XOOPS website spiel, wrong maybe, that XOOPS is a cms that can upload (using a converting module??) to a simple html only website that a community organisation/ very small business can only afford (as php and MySQL cost many extra $$$ per year). Can this be done or did i misread the spiel?

webdude, welcome on the XOOPS forum!

I don't know exactly what you mean by 'spiel' (= game in german?).
XOOPS is a fullblown CMS based on php en MySQL. It is extensible by a lot of modules to perform nearly all functions that could be wanted. You can easily try things out on your local PC with eg XAMPP.
XOOPS is GPL and thus free.
For hosting you need a hoster that offers some space, php and a MySQL database, but you find many for under 100$ a year, domain name included, which is very affordable.