It's not a penalty, at one point earlier this year the situation was that if you arrived without your e visa they weren't going to let you into the country, but ship you back home on the next flight! After much outcry they extended the deadline for the e visa and are allowing people who arrive without one to purchase one here, in manned kiosks. Ok, you pay an extra £7, but would you rather that or turn round and fly back to where you came from ?