Added price multipliers

eco-api/src/main/java/com/willfp/eco/core/price/Price.java

@@ -55,4 +55,22 @@ public interface Price {
     default void setValue(final double value) {
         // Override when needed.
     }
+
+    /**
+     * Get the price multiplier.
+     *
+     * @return The value.
+     */
+    default double getMultiplier() {
+        return 1;
+    }
+
+    /**
+     * Set the price multiplier.
+     *
+     * @param multiplier The multiplier.
+     */
+    default void setMultiplier(final double multiplier) {
+        // Override when needed.
+    }
 }

eco-api/src/main/java/com/willfp/eco/core/price/impl/PriceEconomy.java

@@ -16,6 +16,8 @@ public final class PriceEconomy implements Price {
      */
     private final Supplier<Double> function;
 
+    private double multiplier;
+
     /**
      * Create a new economy-based price.
      *
@@ -51,6 +53,16 @@ public final class PriceEconomy implements Price {
 
     @Override
     public double getValue() {
-        return function.get();
+        return function.get() * multiplier;
+    }
+
+    @Override
+    public double getMultiplier() {
+        return multiplier;
+    }
+
+    @Override
+    public void setMultiplier(final double multiplier) {
+        this.multiplier = multiplier;
     }
 }