How can I get a PDF copy of my receipt for turbo tax payment ? This is ridiculously difficult !

If you have not yet filed : 

How to see your fees
https://ttlc.intuit.com/questions/2565973-how-do-i-review-my-fees-in-turbotax-online     

For help with fees 
https://ttlc.intuit.com/questions/1901213-what-can-i-do-to-reduce-my-fees     

How to remove the Pay from your Refund fee 
https://ttlc.intuit.com/questions/1900517-how-do-i-remove-refund-processing-fees-in-turbotax-online-and-change-my-payment-method  

If you have filed : 

What did I pay last year for TurboTax?

You received an email from TurboTax if you paid the TurboTax account fees by credit card.  Look in your email junk or spam folder for the email receipt from TurboTax.

Or -

To access your current or prior year online tax returns sign onto the TurboTax website with the userID you used to create the account - https://myturbotax.intuit.com/

Scroll down to the bottom of the screen and on the section Your tax returns & documents click on Show.  Click on the Year and Click on View order details

Or -

When you sign onto your online account and land on the Tax Home web page, scroll down and click on Add a state.  See screenshot

This will take you back to the 2018 online tax return.

Click on Tax Tools on the left side of the screen.  Click on Tools.  Click on My Fees