Goshiwon or share house for a first semester?

You are not romanticising it. For someone arriving alone with no network, the social side is the single strongest argument for a share house, and it is worth more than 100,000 won a month.

What a share house gives you that a goshiwon does not:

1. People who notice you exist. In a goshiwon you can go a week without speaking to anyone in the building. In a share house you run into flatmates in the kitchen every day. In month two, when the homesickness lands, that difference is not small.
2. A real kitchen. You can cook properly, which changes your food budget and your diet.
3. A common area, so you can have people over.
4. Often a mix of Koreans and internationals — ask about the current mix, because a share house full of foreigners speaking English gives you the cost without the language benefit.

What you give up: privacy, quiet, and control. Shared kitchens get messy, flatmates have schedules, and if the house has a bad dynamic you are inside it.

The money: 100,000 more a month is 1,000,000 over ten months, plus a 300,000 to 500,000 deposit you get back. Against a first semester where you know nobody, that is a reasonable price for a built-in social floor.

When the goshiwon is the better call: if you need silence to study, if you already know people in Seoul, or if you are certain you will be out of the room constantly.

One question to ask before choosing a specific share house: how many people, and what is the current nationality mix. A four-person house with two Koreans is a different product from a twelve-person house of internationals, even though both are listed as share houses.