I don’t think their patties have changed size any, though I wouldn’t swear to that. Also, at least in my area, BK regularly sends out pages of coupons in the mail. I think with the coupon you can still get a large sized Whopper meal for around $7. Without a coupon (again, in my area, maybe not all) you can get a Whopper Jr., 4 pc nuggies, small fry and small drink for $5.
I don’t eat fast food much but I am a bit of a BK Stan. So much better tasting food than the clown house.