Why do I have to buy premium twice?

I like this app but why do I have to buy the premium version on my phone then pay again to have it on my computer?? If I only had to pay for it once it would be a good app but paying for it twice is definitely not worth it. Glad I bought it on the phone first since that’s way cheaper then the desktop version!

Catie1234 about Debit & Credit, v1.7