"You get what you pay for!" Use that saying. It is true. It's like firearms, sure you can buy a $100 shotgun. But the craftsmanship, the quality of materials, and the feel of it will be less than desirable. That shotgun will also not last as long because of the sub-par reasons mentioned above. If however you spend $10,000 on a shotgun, it will be made with the highest craftsmanship, the strictest standards, the best materials, and will feel as if it is an extension of one's own body. It will also last a life time.
The same goes with anything and especially with a piano. Why spend $600 on something that will only last you 5 years (or less depending on how much Rachmaninov you play on it

)?
A lesson to be taught and learned is that one should buy the highest quality "thing" (whether it is a shotgun, a camera lens, or a piano) that one can afford. But just to have a piano regardless of the price is a theory not to be appreciated. Myself makes a good example: I don't have a piano, I have an old digital keyboard. I could easily buy a $700 upright piano. But I know for a fact that it will not last long or sound that great. Therefore I withhold myself from buying a real piano until I have enough money to buy a quality instrument which will last me three lives.
I hope this helps.
-jg