Any thoughts on my tub issue?

This has been over 12 years of asking... now I am turning to you, the experts. I should have come here first. How can I remedy this problem. Any simple and inexpensive solutions?

This is a long story but I am going to keep it short and simple. Our tub cracked along the bottom (see photos) a long time ago and we've asked everybody and anybody for ideas... The only idea we've gotten is to tear out everything and replace it to the tune of $12K upwards to $20k. This is from carpenter and construction friends. They just shake their heads.

We asked the marble company and nothing. Its onyx I believe. Bath Fitters can't do anything but replace everything. Their estimate was $15K.

Here's some photos so you can see the carnage for yourself.