The judgment below

The part against the Defendant is reversed, and that part of the case is remanded to the Seoul High Court.

The grounds of appeal are examined (to the extent of supplement in case of supplemental appellate briefs not timely filed).

1. According to the reasoning of the judgment below and the records as to the ground of appeal No. 1, the Minister of Construction and Transportation, on July 22, 1997, designated and publicly announced the area of housing site development under the Housing Site Development Promotion Act as the planned area for housing site development under the Housing Site Development Promotion Act, and designated and publicly announced the Defendant as the project executor of the said housing site development project (hereinafter “instant housing site development project”). The Defendant set the unit price for the housing site to be specially sold to the persons subject to relocation measures pursuant to the rules and regulations on the establishment and implementation of relocation measures, which are internal regulations, at KRW 594,920 per square meter, by setting the unit price for the housing site to be supplied to the persons subject to relocation measures, taking into account the individual matters of each migrants’s housing site, and then setting the unit price for each migrants’s housing site by applying the difference of supply unit price to the unit price for supply.

If a business entity individually determines the sale price of a resettled housing site by applying a gap within the discretionary scope, it may be deemed that the development cost of the entire resettled housing site was differentiatedly allocated to each resettled housing site in accordance with the conditions of the location. As such, in calculating the development cost of the individual resettled housing site, the installation cost of basic living facilities, and the reasonable sale price accordingly, it shall be calculated by reflecting the gap.

Nevertheless, on the grounds indicated in its reasoning, the lower court calculated the reasonable sale price based on the cost of housing site development and the cost of installing basic living facilities without reflecting the gap between the relevant migrants’ housing site. Based on this, the lower court calculated the Defendant’s unjust enrichment against the Plaintiffs. In so doing, it erred by misapprehending the legal doctrine on the scope of unjust enrichment from the cost of installing basic living facilities.