Ask HN: Is the price tag on premium domain names reliable?

I recently wanted to register a name under the .online TLD, and found out that it was a "premium" name with a hefty annual price tag. The price was economically viable for me, but I abstained in fear that the owners of "commercial" TLDs might be free to suddenly incur a massive targeted price hike for a specific name, for example if they saw that the site became popular and was doing well, implicating it as a good subject for "ransom".

Does anyone know of any cases of this happening, or know if this behavior would be a breach of some fundamental rules of ICANN or similar?