Pay whatever you want for the €0+ Stories.
Other stories that cost more are early access which aren't fully uploaded to Deviantart yet. (DA: https://www.deviantart.com/reiko-samaa)
And of course don't share early access stories until they're fully uploaded please.
Also, if you wanna give small tips feel free to use Ko-fi insteadt, i get more out of smaller tips there^^° https://ko-fi.com/reikosamaa