Why am I being charged an extra $79.98 this year for the deluxe edition just because I have a single T5008 slip?

I don't recall this from any prior years....

Getting started

If you are using TurboTax Online, you are charged based on what is on your return. So, if you purchase Deluxe, but need to enter something that is not included in Deluxe, then you will need to upgrade.

 

Perhaps last year you used TurboTax CD/Download instead?