Why did Mary move?

[Eva Elisabeth]

In Mr. Fazio's book, I came across a question I've had myself before - why did Mary Surratt move? The usual explanation is "for financial reasons", but I don't entirely understand what difference the move made. If I understand correctly, her husband had already rented rooms at the DC boardinghouse, so this was not a new "source". And I can hardly believe Lloyd paid as much for leasing the tavern as the Surratts made themselves with (in?) the tavern business. Plus I guess life in DC was more expensive even back then.

Can someone please explain? What do you think as for the "why the move" ?