i did 3 months of testim and it was expensive, but there is
goodrx.com to help you figure out which location is least costly. all you have to do is show them the coupon and they ring it up at a discounted price
even though it was more on the expensive side, i feel like starting off on gel was good for me. i have severe anxiety (which lessened after starting t) and the mental changes can definitely shake you up a bit. i'm currently 6 months on t (3 months on injections now) and i just went through a bad spell of depression and an increase in anxiety, but i'm doing better again.
if your boyfriend is mentally stable, i think it would be okay to do injections. if not, i do think that the (approximately) $600-800 dollars spent for three months is worth it. transitioning is a big deal, but it's not unmanageable.
good luck to both of you!