Galaxy Research said in a report that the vast majority of Bitcoin rollups will be unsustainable. Due to transaction fees, Bitcoin Rollups require millions of dollars per year to maintain. Galaxy wrote: "Each individual data publishing transaction can take up to 400KB (0.4MB) of block space, effectively taking up 10% of the entire block." Since there will be multiple Rollups, and data is expected to be published every 6 to 8 blocks, Rollups may quickly push base layer fees to new highs and make small transactions too expensive. Given the competition for block space, only Rollups that can generate the most fee income and pay block fees can maintain operations.