The cheapest Aluminium brush is 141 Euros inkl. Tax. So minus the 20% VAT for Non-EU citizens that would be about $131 with the current exchange rate. Titanium is approx. $250
That's a reasonable response. Metal, soap, water - doesn't seem like a good combination. However, some metal - like aluminum - is surprisingly grippy, even when wet. The ribbed design makes handling easier - and no less prone to slippage than the usual acrylic handle.
I do believe that one of these are vital to my continued good health. Yes, I feel I have a small aluminium deficiency...