"I think the price tag for pdfs should be no more than 25% the cost of the printed book."
I would say closer to 10-15%, at most.
I still have printed copies of RPGs from the early to mid 80s that are in good condition. Many are worth much more than I paid for them at the time. That's never going to be true for PDFs and ebooks.
Honestly, while there is definitely a greater cost to create printed material versus PDF digital material, more than 50% of the cost is cover art, interior illustrations, cartography, writing, designing, editing and page layout. Why should a digital product that costs 50% the price of a print product to create be sold at 10 - 25% the print product price tag? If there are multiple print runs of a given product, the cost to create gets proportionally less, however, there is no cost savings in the first print run - which most print products only get a single print run.
In general publishers make less money with print products, than with digital only versions of the same products, so only very large print runs and subsequent large numbers of product purchases can produce viable levels of income. Most publishers cannot afford large print runs, only the largest companies - FGG, Paizo, WotC. So while smaller publishers would like to compete in the print market, its almost too costly, yet the market still often prefers print to digital at this time. So smaller publishers struggle to compete. If the expected digital product cover price was only 10% of the print product cost, smaller publishers cannot compete with anybody and is likely to fail as a business.
Is giving you an unrealistically low digital product cover price more important than the survival of small publishers? Is insuring that China gets even more of our money, a good thing for the west? I think not.
Consider that I do game design/development/publishing as my evening job, while I work in the print industry in my day job, so I know both sides of the cost equation for print/PDF product creation.