Withstanding one atmosphere is certainly not an unsurmountable challenge but given the dimensions and given that this thing is supposed to be cheap it is also c

Withstanding one atmosphere is certainly not an unsurmountable challenge but given the dimensions and given that this thing is supposed to be cheap it is also certainly not a negligible issue. You also have to maintain the quality of the vacuum, possibly in presence of expansion joints, and you have to deal with the consequences of a loss of vacuum for whatever reasons.