Personally I dont ever pay more than $3 per retro when they are loose or $4 for the rainbows. You will find they may sell faster as a group as people may wish to save on shipping. They seem to run at 1/2 the price loose as they do MIB.
Perhaps $2 for each of the blind bags as they can be converted easy to key chains by someone. The stick $1 - being without backing looses the flat stickers a lot of value.