Variable Price is an add-on for the Checkout for PayPal plugin that can be used to add a price field to your PayPal smart payment buttons. This lets buyers set the amount they will pay for your products. It can also be used to accept PayPal donation payments.
PayPal
Checkout for PayPal WordPress Plugin
Checkout for PayPal WordPress plugin connects PayPal to your WordPress website and makes e-commerce available for you. With this PayPal plugin, you can create smart payment buttons with a simple shortcode to accept PayPal payments from your customers.