Good quality scented candles are expensive, and there’s a good reason for that. Their wonderful scent comes from essential oils and natural fragrances. They are hard to produce, and that makes them very expensive. Also, the producers need to put a lot of these oils in candles to get the necessary scent intensity.
Scented candles you can find in dollar stores mostly have chemicals to imitate natural scents, and they do it quite badly. Do you really want more chemicals flying around in the air? And even if you run into a candle with natural oils and fragrances, they have so little of them that you likely won’t even be able to smell them.