If those were the prices for the travel on Y-axis.... pretty sure the parts for the X-axis are going to be a lot more... might take the same approach you are using. At least until I sell the house and can save for such a big $ticketed item... I know I am going to forget which direction is which when cutting... I just know that I will make the same mistake again... fixing/replacing the actual parts will help me minimize the impact those mistakes have on the piece that I am working on...
But (and I am just writing out loud here) the thing is, I do not do any critical part that can't be redone if I goof up... even if I have to make it several times it will not be thousands of dollars. I just need have extra material for those times when it happens... I will still be ahead, cost wise, than replacing the lead screw and nut...
As you can see, I do try self-talk to get me out of buying parts... I try, but never seems to work. I really like this machine and want to have it as pristine as I can... you know, for the next owner that gets it when I die