The cost comes from the continuous washing and waves of nucleotide additions (reagent costs). Illumina's technology suffers the same difficulty. The promise of PacBio's technology is that it does not require this continuous washing and staggering of nucleotide additions (unfortunately PacBio was not able to translate its technology to high-throughput high-accuracy or manufacture properly its version of "chips" [SMRT cells] for Single Molecule Real-time Sequencing). I'm afraid the cost will not come down significantly for iontorrent or illumina without a fundamental improvement in reagent utilization techniques or reduction in reagent costs.