The definition of a "luxury car" is rather hard to pin down. Most people think it has something to do with price, but that's not the case nowadays.
These days you can find lots of cars with sticker prices starting at less than $30,000. Most of these offer the sorts of qualities others pay more than $40,000 for high-end luxury brands.
For instance, there's the Buick Regal Turbo. This car offers an enviable balance between laid-back smoothness and gutsy performance, along with a well-appointed and tightly assembled interior. One could wish for more -- like a "Sport" mode button that provides a more tangible change in performance -- but there is still the upcoming high-performance Regal GS to look forward to.