Context: the girls need to hide in a shop run by a man who always makes them buy something if they go in in normal times.
If they took refuge in that shop the blow to Maruko's meager wallet could not be avoided.
I don't know how to interpret ただでさえ in this sentence. The dictionary says "at the best of times" but that doesn't fit with my translation. It only works if I omit the conditional phrase: "At the best of times the blow to Maruko's wallet could not be avoided".
However, I'm not confident about the rest of my translation. I'm unsure about さけられない. Is the verb actually 避ける? Is it potential or passive? I've used both which makes me think I've got it wrong.