Welcome to the community!
Firstly, Fido is not charging interest. The full cost of the device is $720. To finance the device over 2 years: $720 ÷ 24months = $30 per month. That is the monthly amount they are charging for financing the device. If they were charging interest, the total cost of device after financing would be greater than the full outright cost of the device. That is not the case.
@Findingmyway wrote:...You can go get the exact same at Best Buy for $550. ...
Ae you sure you're comparing similar devices? It appears you stated the cost for the 128 GB version from Fido. You should note that Best Buy has two options for a 128 GB iPad 8, one version is Wifi-only and the other is the Wifi and 4G LTE (cellular version). The Best Buy price you quoted appears to be for the Wifi-only version. On the other hand, since Fido is offering their tablets with a data plan, their version would be the cellular version of the iPad. The Best Buy cost for their cellular 128 GB version is $719.99.
When comparing the costs for the cellular versions of the iPad 8 from Fido and Best Buy, the costs are very similar.
Hope this helps 😀