You think parking is steep, wait ’til you see what you’ll be paying for fuel. Hopefully someone else with deep pockets is picking up the tab.
Atlantic is at the approach end of 19C; Signature at the approach end of 19L. Potomac TRACON will get you where you want to go if you let them know early enough in the approach. Crunch times are around 0700-0830, noon-ish, and 1400-1700 for international arrivals, with the latter the busiest. 19R/1L is usually only brought online for afternoon arrivals if capacity requires. 30 used almost exclusively for departures.
KHEF or KJYO certainly much cheaper options but I assume like in real estate, location is king.