How to Deal with surplus high end GPUs (AI computing)

If a business or startup has surplus high-performance GPUs used for AI training and inference—such as A100, H100, or H200—what are the best ways to deal with them?

Are there recommended platforms, marketplaces, or companies that specialize in purchasing or reselling such GPUs? This could be particularly relevant for startups, small businesses, or organizations transitioning to upgraded hardware. Insights on maximizing value while selling or trading them would be helpful!