Casio WK-110

For that price, you get astonishingly much of a keyboard. However, its lifetime is not very promising if you tend to use it a lot. I've only had mine for 4 months now, but some of the keys have started to make clicking sounds when pressing them, so now I have to play with earbuds covered under earmuffs to be able concentrate fully on the music. Besides, a buzzing sound has started to accompany the notes at lower frequencies.