Blimey thats a big difference, I have a load of boxes up in the top of the garage that I had bikes/wheels etc sent to me I just popped me head up there and measured one?
I sent a complete 18" Kona to Australia for £102 in a box 102cm x 68cm x 20cm with parcel2go.com
when shipping abroad often it's not the weight that's the problem but the dimensions - try and get it into the smallest box possible as you'll find a lot of them will charge the same up to 25kgs for a given size box.