Split of refund between spouses who don't share money

Would be curious to hear thoughts on the following situation:

Person A and B are a married couple with no dependents but significantly different income. Person A accounts for 80% of the taxable income.

If they were to file MFS, Person A gets a refund of $1,500 and B would have a balance due of $4,000

If the couple files jointly, the refund is $3,800.

How do you split this fairly?