You're selling an apple pie for your own currency piecoin. If I to buy a pie from you I have to buy x piecoins first to match your price whatever it is. My need of a piecoin is defined by the need of our settlement for a pie ('right' price). Usually, pie like yours costs $5 so I have no incentive to pay more for your pie. If your price for a pie is x piecoins then I will buy x piecoins for $5 and 1 piecoin will cost me x/5.

'Wrong' part of a price is about modelling other people need for piecoins which in turn is about modelling need for pies and other people speculation and that's can be incredibly complex. As you can easily see 'wrong' part of a price makes your coin shitty currency.