After three months of war, how to understand the "10,000 gold" in the couplet "Letter from Wang Jin"?

1, a letter from home on the battlefield is so precious that it can't be exchanged for ten thousand gold.

2. Expressed the soldiers' deep thoughts on their loved ones on the battlefield, and also expressed the author's thoughts on their loved ones.

3. Secretly explain the cruelty of war and the author's aversion to war.