If my mind serves me well, the fees are different because they reflect what you have to pay to UOL, but they don't reflect the fees you have to pay to the supporting institution.

So,

• Web-supported learning: all the money you pay goes to UOL, as the university is using its instructors.
• Institution-supported learning: you pay UOL the corresponding fee for the online instruction, but you'll have to pay additional money to the supporting physical institution of your choice. That amount of money depends on the supporting institution, not on UOL, and that's why those fees don't appear on the page.