Forty five more gold pieces
Obtain the sword from the fortune teller during the first scene. Press Pause(73) on controller two to collect more gold.
Level select
Press 1, 1, 2, 2, 1 + 2 when the level and stage numbers are displayed.
Level select (European version)
Press Down + Start at the title screen for a level select feature. Press Up to select a new starting level.
Play The Japanese Version
Insert the Wonder Boy in Monster Land cartrige into your Master System. Before you turn on the power, hold down buttons 1+2 and the little black button on the middle of the d-pad and turn on the power. If done correctly, when the game comes on, you should see the words "Sega Mark III" and then the game will be in japanese and will be a lot harder.
Forty five more gold pieces...