Yes, they are worth the cost, but they are not indestructable thats for sure. I figure I use 3-4 quality alloy shafts a year or two titanium shafts. Assuming two alloy shafts cost the same, if not more than one titanium shaft, it is worth making the investment in Titanium.
i have had my trusty warrior titan pro pole for 4 years now and i like to throw some pretty aggressive checks at times and it is holding up well. its bent and dented but hasnt broken yet!
I use a Brine Titanium Powergrip and it is the best shaft I have ever owned. It has about 4-5 dents less than a centimeter wide and a millimeter deep. It has taken some serious abuse at attack over the past 2 seasons. Ebay $45.
im not sure which position you play, but if you play defense i would recommend one. i play D and i have a platinum allow which is bent and full of dents. as a middie i would recommend the lightst one you can find, and as attack it would be good if you take a lot of punishment.
if your son is just entering the highschool level it may not be a bad idea because it could last for a long time. ive found that its usually not a good idea to skimp out on equipment