You must have had a lot of packaging, plonka. $1.20 equals 125g or less (including the envelope), $1.80 250g. So a max of 375g.

Plus the cost of the envelopes, so not quite $10.00 more.

As a matter of interest, a B1 box with click & send costs $1.75 for the box and $6.50 postage, and the weight limit is 15kg. So you could have sent the items properly protected for $8.25.