I've always been a big fan of Baymard and their ecommerce research. Recently they posted an article about showing shipping costs on product pages - It's worth a read
https://baymard.com/blog/show-shipping-costs-on-product-pages?
About Fraser Clark
I've been a professional developer for over 10 years. I've been consulting and developing websites & software for small businesses, multi-nationals & governments.
I'm an expert in WordPress, Drupal, Laravel & a whole host of other platforms.