Well, as I wrote already above, persoanlly I do not really like the optics of the spheric masks (regardles if it is Sphera or this one), so use a normal mask (mostly Technisub Mikromask) when the vision is importnat and I really want to see something. I agree with Azapa that it feels as if you were drunk when using a spheric mask, and the vision is somehow not consistent. Perhaps it is individual, because I also know people using it for everything, including spearing, or UW rugby, where good vision and distance estimation are esential.
As for the tinted lens - it is not too dark, and if it was not banned at freediving, I'd definitely take one. Whether you can spearfish with it, I have still my doubts, but the tint won't really mind - unless you fish in very bad light conditions.
As for the shipping cost - as I wrote above, I believe it should be possible to send for under 5€ in EU, and below 10€ worldwide at a single mask and without insurance or tracking number. Double of it if with insurance and a tracking number. At multiple masks, the shipping cost per mask would be lower.