If the leg ‘ulcer’ is growing, I’d be concerned. As I recall the many, many times I’ve had the 'wtf is this bump???!!" conversation with vets, a biopsy of any given part of a bump is inconclusive; you might have just missed the malignant cells. A second opinion seems like a good idea.
I had a leg bump taken off my 65lb dog when she was around 12; she was fine, but it aged me. It was also a weirdie little spot that came and went, and which she licked sometimes (her allergist noticed it first), and I just couldn’t take the not knowing anymore. It came back benign, but I was relieved to just have it gone, and she never licked the area again.
$2k sounds a little high, but not by much. My dog had 2 large bumps removed last year (at 16!) and the cost was about that, all told - drugs, supplies, IV catheterization, bloodwork, the cost of a surgeon’s time, etc.