If 4th Edition books are going for well over three times the PDF price, certainly somebody is buying them. I mean, if there's no audience for an L5R reprint, there's no audience for a 5th Edition either if it doesn't cater to the baked-in audience. I know my group has four people who would buy one if they could get it on Amazon for less than $120. None of them will by 5th Edition at this rate and they definitely haven't bought the PDFs. I was listening to one of the currently running Twitch streams, and 3 out of the five players were jealous of the other two's hard copies of the rulebook. Even the GM didn't have them. Clearly there are people who want to buy it. That's why FFG has to decide what it wants its game to be and cater directly to that audience. Because it owns 4th Edition. Heck, they could even just offer a pre-rdered custom printing for 4th Edition and still move enough copies to justify the print run. I'd bet you'd have people buying multiple copies just to speculate on the secondary market since clearly 4E rulebooks have value based on rarity and demand.
This isn't Star Wars. L5R doesn't sell itself.