Change woocommerce sales price programmatically

wc_change_sales_price.php

<?php
// Your Product ID
$product_id		= 57;

$ecd_product	=	new WC_Product( $product_id );

/**
 * Check if product exists
 */
if( $ecd_product->exists() ){

  /**
   * Get current (discounted) sales price for calculations etc
   */
  $ecd_product->sale_price;

  /**
   * Get regular price for calculations etc
   */
  $ecd_product->regular_price;

  /**
   * Get price (the actually price that people will pay)
   * NOTE: If you set sales price different, this should be same as sales price
   */
  $ecd_product->price;

  /**
   * Update sales price to $10
   */
  $sp	=	update_post_meta( $ecd_product->id, '_sale_price', '10' );
  $p	=	update_post_meta( $ecd_product->id, '_price', '10' );
  $rp = update_post_meta( $ecd_product->id, '_regular_price', '10' );

  if( $sp && $p ){
    echo 'Sales price is $10 now!';
  }

}

Perfect code

thanks mate

Better add one more update_post_meta with _regular_price because wp_postmeta contains 3 prices: _price, _sale_price, _regular_price
like this:
$rp = update_post_meta( $ecd_product->id, '_regular_price', '10' );

incomplete function, i think it is, to which hook it should be hooked in woocommerce

This code worked for me
I had to update and set static price for every single product in woocommerce.

 add_action( 'added_post_meta', 'ij_set_default_report_price', 10, 4 );
add_action( 'updated_post_meta', 'ij_set_default_report_price', 10, 4 );
function ij_set_default_report_price( $meta_id, $post_id, $meta_key, $meta_value ) {
    if ( $meta_key == '_edit_lock' ) { // we've been editing the post
        if ( get_post_type( $post_id ) == 'product' ) { // we've been editing a product
            $product   = wc_get_product( $post_id );
             if($product){
				 $rp = update_post_meta( $product->id, '_regular_price', '4200' );
						update_post_meta($product->id, '_price', '4200');				 
				 
			 }
        }
    }
}