I was going to say, 150mg of methotrexate might kill you! lol I was taking oral methotrexate but I got terrible side effects from it. I had to take it on Saturday mornings and my whole weekend was always ruined because I felt like death. It was a specific reaction to the MTX. When I switched to the injections I didn't get any of those side effects, and only got a few headaches at the beginning. My worst symptom from the injections was the occasional night sweats that' just an annoyance.
As far as the costs, the syringes are only 20 cents each, and while I don't remember how much the pills will, the injections weren't expensive. I guess it's different too because I have medical coverage.
Also for me, the injections seemed to be much more effective. It's super easy (I did them myself) and the needle is really small so it's painless. I do however look like I have a "Connect the Dots" puzzle on my leg now though from doing the injections every week