Charles: It cost about $0.85/ea. Tons of hardware and software programmers on the Internet. It is a one time programmable device but your development can be done on a compatible reprogrammable device such as the PIC 16F84 or 16F628 (1/2 price [$2.50/ea]
I do not know what volumes you are pricing, but at 100 the LPC90x are about $0.50 and have reprogrammable flash.

Jez:I have to agree with Charles,most of the 52's strengths lie with it being am 8 bit micro and its external addressing scheme,take that away and there is not much left The external addressing is more and more a thing of the past, most new derivatives have ERAM and internal flash.

While the '51 may not be the best for 8 pin designs, I would not rule it out without knowing the application.

Erik