75 is spot on IMHO, maybr even a little low. I mow .25 acre lots for around $30 usually. Depends on multiple factors. Everyone has different expenses, but her old lco definitely just stopped showing up. 50 is way too low for that much land.
Lawns that big are a pain by yourself, and this woman is just trying to find a sucker to mow it for less than her already very reasonable price. Glad to see you have the strength to say no this early on. Not a lot of guys do, I certainly didnt. Only said no once my first year when a guy wanted the worst clean up I've ever seen done, and he needed it done by the following weekend. I said 900, he said that's too much, I said its probably not enough and walked back to my truck. The dump bill alone would have been over $100. Dillusional.