chipfoundry.io charges $14,950 for packaged 100 chips. As far as small batch manufacturing goes, that's reasonably affordable. $149 ea. Occasionally I see better deals crop up as part of group buys or for bare dies. Presumably, one would prototype their design on an inexpensive FPGA board first, to verify functionality. So as to be reasonably sure the first batch of chips worked. Folks like Sam Zeloof are working to build new tools for one-off and small batch designs as well, which may further reduce small quantity prices.