Sad news

This morning I noticed a lump in one of my rats. It was pretty much instant heart break, I am very aware of how common tumors are in female rats and I know how aggressive they are.
So after freaking out for a few mins I decided to take her to the vet.
When Todd and I got there I tried to explain what was wrong to the nurse and I just started crying. I felt like one of those really annoying kids that get hurt at the park and then they pick themselves up, but when their parents arrive they start crying again like its the worse fucking thing.
So the vet came down from the surgery and had a look at Little Pup and he agreed that it was a tumor.
He said I have 2 options , first was to have a surgery to remove it that will cost $300 , but he said chances are it will grow back quickly and the second was to let her live it out. I also asked if about having her put to sleep , but we decided we would let her go on until it inhibits her normal life.
I feel so fucking stingy deciding not to pay the $300.
The only reassurance I got was that she isn't in pain or suffering. I'm also feeling a bit of guilt for not spending  more time with her.