Well, DA 50 is $5.oo cheaper than Evolution 45GX, and puts out more thrust then Evolution. On the other hand E 58GX puts out stanning 8.5Bhp(I thought it is a missprint when I first read specs). What bags my mind that 45GX and 58GX cost the same $600.00. If 45 were somthing like $495.00 that would probably put DA out of biz, but this is never going to happen.
You are correct about the DA 50 being cheaper, but as far as thrust the 45GX is not that much less power than the DA. And you must take into consideration that the 45GX is in the 40cc class of engines, If you compare it to engines like the Fuji 43, the ZDZ 40RV, BCMA 40, and SPE 40 the Evolution 45GX will clearly prove superior. The Evolution 45GX will spin a Bolly 22X10 at 6900RPM which translates to over 27Lbs. of thrust at standard temperature and athmospheric pressure.
I do agree it doesn't make sense that the 45 and the 58 being the same price, it comes down to what you prefer as far as size and power to weigth ratio.