Brightness Group

Woocommerce product backend page add markup(%) field in which add percentage which you want to increase price of product using plugin. if you want to decrease by some percentage add markup(%) field value as nagative.
eg. 
1) Product price $150 and if increase value by 20% in backend add 20 and its display price in frontend $180. 
2) Product price $150 and if decrease value by 20% in backend add -20 and its display price in frontend $120.
<h4>Required Plugin</h4>
Woocommerce

Product Price Markup for Woocommece

Price increase by percentage for WooCommerce Shop product.

darrinb

Easily include raw markup languages (HTML, CSS, PHP, etc.) in posts using custom quicktags. No need to encode, the filter does it 
for you. Creates convenient “encode” buttons for post authors in the HTML editor.

Product Price Markup for Woocommece vs WP Post Encode