Two Catholic charities that launched the first appeal to the Charity Tribunal face legal costs of £120,000.
Mark Wiggin, chief executive of Catholic Care (Diocese of Leeds), which lost its appeal two weeks ago, said its costs were about £75,000. Father Hudson's Society, which withdrew its appeal after a directions hearing, had spent about £45,000, Wiggin said.
"There aren't many charities with reserves for that kind of expense. We have a base of Catholics who support us, but not every charity has that."
Wiggin said the trustees of Catholic Care, which had an income of £4.2m in 2007/08, had not yet decided whether to appeal to the High Court.
The charities had appealed against the Charity Commission's refusal to grant them permission to change their constitutions, allowing them to exclude gay couples from adopting children.
Tribunal president Alison McKenna said when it opened last year that the tribunal would offer "low-cost access to justice".