If you just used lead the billet would be 31lb, it'd be procurable and shippable for under $100.

Osmium is about twice as dense so yeah that would still be shippable at around 60 lb... I don't think that's even tens of thousands at that point? Isn't it going to be in the millions? I'm just thinking that like if you went for gold instead, 50 lb is 800 oz, at $3300/oz these days doing this with gold is $2.64M, no? And surely osmium blows gold out of the water by like 10x, right?

Jokes on you when the $100 of insurance is all you get back from the post office...

Edit: a sibling comment points out that you can probably do this under $100 with tungsten too and get up into that 50lb+ range.