Space Colony is halfway between Startopia and The Sims. It takes place on a planet surface, but really, the whole core is there.
Okay, maybe 3/5 of the way towards The Sims. If you hate Sims games, you won't like it much, but if you're neutral, give it a shot. The economy will be simpler than what you're hoping for, but maybe you'll like the time management aspects.
I found it when I was looking specifically for Startopia-like space station sims, myself...
...If you're willing to look a little farther out of the genre, Outpost 2 is a planet-side game that is halfway between Startopia and (your favorite RTS here). I recommend it a lot, if you like Space Colony, though it's a little dated now and will run a little funny. A typical day in Outpost 2 is sending a bulldozer out to the distant plateau where your surveyor found high mineral concentrations, so that it can pre-pave your building sites so you can get set up faster; your vehicle factory is churning out an extra construction vehicles so you can load up a nursery in addition to the vital command center, structure factory, vehicle factory, and smelter when you set up your new base, while you're frantically loading the structure kits onto your existing ConVecs and managing your ore hauling trucks to do a couple runs to your backup mine before the FREAKING VOLCANIC ERUPTION pours lava onto your primary base. Meanwhile you've just researched better seismology so you have advance warning of earthquakes, and you've just re-tasked your labs onto faster scientist training time. Then you find out that, while all this is going down, Plymouth colony has sent a couple combat vehicles over to say hello under cover of darkness...Outpost 2 has a pseudo-fog-of-war, you have satellites so you can always see everywhere, BUT there's also a day/night system and you can turn off your vehicles' headlights to keep them from being highlighted on the map at the cost of halving their speed (naturally, nice, cheap light towers at distant choke points are a good defense against someone sneaking up on you that way).
Yeah, Outpost 2 is a hectic management game in campaign mode, and a blast in multiplayer. Plus it came with an in-game novella that advanced at about a chapter per campaign mission. Pity it's about ten years old now.