I am very lucky, I see T in a clinic for $10/session, and it is covered by insurance. But if I were in a similar situation as you, I would have to weigh the cost of therapy to the benefits. If you feel like you are making a lot of progress with this T and that it would be very beneficial to stay, maybe you can talk to your T about a special rate. I know many T's do this. If you feel maybe stagnant in therapy, or that the high rate is not worth the quality of therapy you are getting, maybe it is time to move on to a new therapist who is cheaper/covered by your insurance.
It's always rough when finances get in the way of health. It shouldn't be that way.
In terms of therapy ending... I don't know. I see my therapist in my university clinic, so I suppose it will have to end when I graduate. But if it needs to end before then, how will I know? I've never discussed it with my therapist before. All I know is that I'm definitely not ready to leave therapy right now.