Time is generally represented in person-hours, which correlate well to team size necessary to get a product out the door. Most individuals or tiny teams can't afford to spend multiple years working on something alone.
Story of my life!
Googling says ConcernedApe spent about 10 hours a day, for 4.5 years, and let’s say he took a day off here and there, you’re looking at 10,000-15,000 man hours to deliver Stardew Valley.
So that’d be around $500,000-1,000,000 (likely higher) if you had a team working on it, paying them all $100,000 a year, to get that many hours out of them.
Making things on a team definitely makes things a lot more expensive!