Of course there are some exceptions. Like Balatro selling 5 million copies (1 developer + 1 composer), the Touhou Project series (solo dev), Slay the Spire (two devs, ), and Terraria (11-person studio, 9'th best selling game of all time with 60,700,000 copies sold as of November 2024).
The big studios seem to like spending a ton of money on games, but there continue to be new IPs created without a massive budget or marketing campaign.