I'm guessing your underestimating the amount of shops carrying Jens hardware. I did some poking around when i was trying to locate a 1230/56MHz for my self. But even at that your pretty much saying it your self. It's hard to get the numbers of a single unit up around the 4 figure number. And have hours of RnD in a product that you suspect isn't going to sell in more then in the low 100's... Perhaps when everything else is said and done. Like a last great hurray. "Better to end with a bang" but i doubt it.
The ACA 123x is probably pretty much "the same" design, with more or less tweaks to allow for different speeds, and the later reincarnation. The card for the A600 i guess is a product from a independent RnD process, as will the ACA520 be. And so on. And if he has trouble justifying a ACA for CDTV's, the AGA MKII for A4000 and so on... well, i guess a ACA1260 is in the same numbers. Bottom line is, if the hardware was free he could probably manage to sell the units to recover RnD, but the hardware is just the opposite, a 68060 is darn expensive...
Either way it's pure speculation. Jens has the numbers, but i doubt he is willing to share. I probably wouldn't be.