That's an excellent point! On that topic I recently listened to an interview of the founder of EleutherAI, who focuses on training small language models. She said they were able to train a 1B parameters reasoning model with 50K Wikipedia articles and carefully curated RL traces. The thing could run in your smartphone and is at parity with much larger models trained on trillions of tokens.

She also scoffed at Common Crawl and said it contained mostly cookies and porn. She had a kind of attitude like "no wonder the big labs need to slurp trillions of tokens when the tokens are such low quality". Very interesting approach, if you understand french I can only recommend the interview.