Wondering if you have used your Wholesale plugin with a product import plugin, if so which one? If not, are your fields store as custom fields or separate tables?
My plugin stores all per product data (wholesale price, wholesale only, product wholesale tax class) as postmeta fields, the same way WooCommerce does. So, any importer that allows you to map to custom postmeta fields should work just fine for importing wholesale prices.
The postmeta key for wholesale price is simply:
_wholesale_price