No need to write plugin for this, we have to do it in xml level
create a layout xml
app\code\MYNAME_SPACE\MY_MODULE\view\base\layout\catalog_product_prices.xml
<?xml version="1.0"?>
<!--
/**
* Copyright © 2013-2017 Magento, Inc. All rights reserved.
* See COPYING.txt for license details.
*/
-->
<layout xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:View/Layout/etc/layout_generic.xsd">
<referenceBlock name="render.product.prices">
<arguments>
<argument name="default" xsi:type="array">
<item name="prices" xsi:type="array">
<item name="final_price" xsi:type="array">
<item name="render_template" xsi:type="string">MYNAME_SPACE_MY_MODULE::product/price/final_price.phtml</item>
</item>
</item>
</argument>
</arguments>
</referenceBlock>
</layout>
Above xml will effect only for simple product if you need to modify the bundle product then
<argument name="default" xsi:type="array">
should be
<argument name="bundle" xsi:type="array">
or in case of a configurable product
<argument name="configurable" xsi:type="array">
create a phtml that is
\app\code\MYNAME_SPACE\MY_MODULE\view\base\templates\product\price\final_price.phtml
Copy final_price from core module and modify it as you needed
to modify other price type you can refer
vendor\magento\module-bundle\view\base\layout\catalog_product_prices.xml
