"This is the valid price."
Translation:Ini harga yang berlaku.
I think there is a subtle difference. If I was bargaining over the price, the seller might say, Ini harga berlaku = This is the (valid) price ... meaning that this is the price I will offer. Ini harga yang berlaku would be what would be said if I queried the price ... e.g. Is this the price with the discount? I may be wrong, but 'yang' usually adds some specific meaning ... but not always.