Hmm, hardly going to be worth it if you pay for 4 flights at short notice. Maybe you could put two boxes inside one larger one, then you'd only have to pay for two seats on the return? I suppose they have a limit on the size, but surely the big box wouldn't be bigger than the average fat passenger? 
You will be amazed how cheap flights from London to Stockholm are + RyanAir serves 2 Stockholm airports, so there is choice.If they give me at least 3 days notice I can probably squeeze inside a budget of less than 200USD if it's not the weekend, which is less than the 240 I paid + quicker deployment + I get to securely transport the miners myself.
Cant you get one thats not fully assembled? Or at least with the casing not bent, like on one of those pictures?
Or disassemble it, I know Id get creative
That would invalidate the warranty + it will be bigger if it's flatpack.
The cheapest would be 2 single tickets on the way back.