The FROG Mk. IV was introduced in late 1932 at 10/6d. By Christmas 1937 it was down to 5/-. To put that in perspective, in 1937 a labourer would have been paid a basic 30/- per week !!!
Sources -
FROG Model Aircraft 1932-1976 ISBN 0-904586-63-6
My angling pal Ernie (aged 87 - farm boy who joined the Army in 1938)
Best wishes to all you survivors - and my undying gratitude.