Whittman-Walker in DC wasn't too expensive out of pocket even before I had got on the sliding scale. With no sliding scale was like $150 for doctors appointments and $50 for 3 months of hormones for me. That was a little while back, but all things considered that was pretty reasonable for a high standard of care with people who were very respectful of my gender identity. I was from Virginia, so MD should be fine I imagine as well.
Edit:
Also while your insurance shouldn't be covered under section 1557 of the ACA (if anything is at all anymore) It seems like MD's state laws should at least protect you. If Healthcare is a public accommodation in MD, then under §20-304 it clearly spells out Gender Identity right? It might be that their policy is very much illegal, but they don't have anyone telling them it violates state law, I would say it would be worth it at least to contact MCCR, and ask them to do an inquiry
http://mccr.maryland.gov/