I think Siku were a little more expensive, but if a remember well actually many of the Majorette I got were not sold with Majorette packaging but as "produit blanc", a "generic" brand from GB supermarkets, I'd guess these were older models (e.g. from a few years before):
http://images.forum-auto.com/mesimages/289456/majorette045.jpg
(29 BEF = about 0.75€)
there were also some from Texaco around the same time:
http://images.forum-auto.com/mesimages/289456/majorette043.jpg