Is an eSIM cheaper than my $10/day "International Day Pass" from Vodafone, AT&T, or my home carrier?

Yes, significantly. This is the #1 reason to buy an eSIM. Most home carriers (from the UK, Europe, Australia, etc.) charge a fixed daily roaming fee (e.g., $10-$15 or £6 per day). This can cost $150 for a 10-day trip. A Cellesim eSIM is a one-time prepaid fee that gives you a large data bundle (e.g., 20GB or Unlimited) for a fraction of that cost.