I think there is a bit more to these more expensive filters than just the quality of the end-result? The weather here, in UK, is very "moderate"; if I was going to more extreme climate (which I am in a few months time) I would want something that is more durable .. I would think even the budget Heliopan would be better suited for climates over 50C than the cheaper filters.
I could be wrong, as I haven't test this ... but I don't want to be stuck out there and wishing I had spent the little bit extra.