> Romania reportedly has unlimited for 4€ but I don't know which operator.
Orange Yoxo is the only one which has actually-unlimited, all the others have a fine-print somewhere with "up to X GB/month, then bandwidth is severely throttled".
I'm using the 4.9€ plan for a mountain webcam[1] and they have been true to their word, no throttling so far.
US plans just aren't comparable as they've been historically f'd with astronomical monthly payments.