Honestly, I spent a year mapping this out before going indie, and the main thing that surprises people is how the cost structure flips the script completely. Traditional publishing looks free—you get an advance, they cover editing, design, printing, distribution. But your real cost is time and creative control. You trade a huge chunk of royalties (often 10-15% on print) and years of your life for that 'free' service. It's a trade, not a gift. Their investment means they own the process; you follow their schedule, their cover tastes, their marketing plans (or lack thereof).
Self-publishing puts the invoice right in your face, but the ledger looks different. You're looking at maybe $2,000 to $5,000 upfront for a solid professional edit, a decent cover designer, and formatting. That's if you hire out everything. You can spend less if you have skills, or way more if you want top-tier marketing blitzes. The difference is, every dollar you spend is an investment you control, and every sale after breakeven is 70% royalty landing in your pocket. The risk is yours, but so is the upside and every single decision.
Where people get tripped up is the hidden, ongoing cost of traditional: the opportunity cost. That book they take 18 months to publish could be earning you reader feedback and series momentum on KDP in three months. I've seen friends with traditional deals watch their book sink with no promo while they're contractually forbidden from self-publishing something else quickly. My upfront cash outlay hurt, but regaining that time and agility? Priceless. It just depends whether you see yourself as a business owner or an artist supplying a factory.