Simple math. He was getting the old promo rate ($74.99) and he is looking at the chart to see what his rate will be after the promo expires ($89.99). The loss of the $10.00 discount, combined with the total of $5.00 in increases, equals a $15.00 increase.
He said his 'regular price' was going up $15 is where I got confused. If your interpretation is accurate and his package price is going up $5 and if he's not happy with the promotional price expiring then he should call DISH and see what they can do for him.