The plastic handle has been made that way to minimise weight and it also contains a foam buoyancy element, however according to Hanter's report it is not a closed cell foam but an open cell type, so not really very good for buoyancy once it takes up water! This foam cell type may have been changed since then, so it is something that you could ask the manufacturer. The plastic handle had to be a clamshell moulding to allow the installation of the trigger, line release and safety lever which is the black item just under the trigger. That way their respective pivot pins can be trapped in the moulding halves during assembly and you do not see the ends of the pins, nor can they fall out.
Their web photos shows plenty of guns in various sizes and they have been around for some years, so I expect that the handle has stood the test of time (so far anyway!). If you think of a typical pneumatic speargun as a clock then this is a watch from the size of parts perspective. I do not think the cylindrical sear is made from titanium, there was no mention in the reports that I can remember, but I may be wrong. Titanium is lighter than steel, is strong and tough, but not good for wear unless it has special coatings. Stainless steel would be better, you require something hard in a sear of this type to avoid blunting the edge of the piston retention step, plus the mechanism is swimming in oil, so corrosion is not a problem.
The gun is relatively expensive to buy, but even though it is a "factory gun" the production quantities cannot compare with those for the Italian models in terms of their sales volume, so less guns produced means a higher price per unit. The most expensive PV models have the power regulator R (10% power decrease) and rear tying of the shooting line M, which I guess means a line slide, otherwise they are single power and a front tied line. Spears have integral tips or thread attached tips.
A reseller in Europe would have to take a portion of the sales price, so if you can buy direct from the manufacturer then it would be cheaper, unless there was a volume discount on unit prices for a distributor. After looking at the high price of the "Airbalete" other pneumatic spearguns now seem cheap, although you do get a reel as standard equipment! If you shoot a really big one then it gets the reel and the gun.