guestx: You seem to be under a number of misconceptions
(1) A great many RISC OS users bought x86 cards at the intended full price, including myself. Usually after they'd already used the basic 486SLC card, and wanted more performance.
(2) Most PC card owners, initially at least, used their x86 cards quite extensively, not just for an occasional application.
(3) It wasn't only the rather sluggish Texas Instruments 486SLC that appeared on a PC card. There was a very wide variety, including 486DX chips at 40MHz, 66MHz and 80MHz, and two different varieties of 5x86 chips at 100MHz and 133MHz.
(4) The investment involved was large, but not colossal (remember it was a joint project with Aleph One, not all carried out by Acorn). The main problem in terms of time and cost was the faults with the first ASIC production run.
Just like a real PC (and unlike the Risc PC), the x86 card add on had a fairly limited lifetime - it was designed to accept 5x86 class processors, but no more. But that doesn't mean it wasn't extremely valuable to a great many Risc PC users during its realistic lifetime (and I do know some still use it now).
Be Inc built an SMP system with twin 66MHz (later 100MHz IIRC) RISC chips, and it did indeed turn a lot of heards in their direction (along with some of their software). But heads turning didn't enable them to survive as a hardware company, either.