A ridiculous amount to spend on folders.
But this is a non-story. I suspect what is actually the case is that the contract they have with Barrow Hepburn & Gale is an exclusive contract. BHG are the supplier of the ministerial boxes which are according to their own website the only boxes that meet standards for holding classified documents.
That is technically the case but can't technologically be the case for a briefcase carrying paper documents.
They don't have prices listed on their website, it's a bespoke service in a niche industry.
It's unlikely to be the ministers insisting that they need the expensive folders, it's what looks like a commercial decision to keep alive a company that is worth a few hundred thousand pounds but which has a long history of supplying the boxes, and would instantly implode if the government business dried up.