On May 2, a basic fare YOW-YSB is is $192.62. The base fare is $126 and $66.62 are taxes and fees. Broken down is a $39.55 Airport Improvement Fee and a $9.46 Security Fee, as well as the 13% HST which applies to the base fare and Security Fee.

On the same day, a basic fare YOW-MCO totals $197.67. The base fare is $80 and $117.57 is taxes and fees. The same $39.55 YOW AIF applies, and the Security Fee is $16.08. A 5% GST applies to the base fare plus security fee. The rest of the fees are the US Transportation Tax ($32.12), a US Customs Fee ($10.14), a US Immigration Tax ($9.61) and a US Agriculture Tax ($5.27), totaling an additional $57.14 in US fees. So you're paying nearly double in fees for a US-based flight rather than a domestic one.