The scope of potential impact from building luxury apartments is wider than a price decrease. It' likely your area has a far larger demand for housing than the amount that is being built + existing housing stock, regardless of type (luxury vs affordable).
Put another way, building the luxury apartments helped prevent an acceleration of price increases across all levels of housing stock. Students from high income families need a place to live, and instead of taking housing stock from the affordable pool, further driving up costs, they have additional desirable supply at their income level.
But! That only prevented price increases due to limited additional supply and was insufficient to drive down costs. Overall aggregate demand still exceeds supply. The simply answer is to build more at all price levels. Small incremental increases of supply are unlikely to drive down costs.
Put another way, building the luxury apartments helped prevent an acceleration of price increases across all levels of housing stock. Students from high income families need a place to live, and instead of taking housing stock from the affordable pool, further driving up costs, they have additional desirable supply at their income level.
But! That only prevented price increases due to limited additional supply and was insufficient to drive down costs. Overall aggregate demand still exceeds supply. The simply answer is to build more at all price levels. Small incremental increases of supply are unlikely to drive down costs.