Around $6 for padded flat rate envelope which we're currently using. I'll have to go through the train and see what's what when I get it back after Dragonpeppers. If we have to upgrade to a bigger box cost will go up. Mfrb is around $12 to ship, might be able to find a different box for cheaper but I like the flat rate boxes. 2 day shipping, $50 insurance and tracking all included. Shipping in another type of box would possibly take longer if it isn't shipped priority and everyone would have to remember to get tracking on it which costs extra. I know $12 isn't cheap but considering the amount and variety of seeds in the train I think it's a pretty good deal. Everyone will only be shipping it only once. Hell a seed order from a vendor can easily be $12 for just a couple of packs of seeds and this baby is packed with as many varieties as most vendors and some things you probably can't get from vendors. Also has powders and such to sample.
In the end we'll put it to a vote if we need to up the box size. Not just my seeds in there so I don't want to make a decision that is going to cost more money without running it by everyone else. But I'll get the train and see what's what before we get to that point but I think this is what's going to have to happen especially since we're starting a new round with new stops which will be even more seeds. Mfrb is pretty big and I don't think we would ever have to go up from there. Oh and we ditched the sfrbs inside the padded envelope a while back so it's all seeds inside that baby.