I love our #corsirosenthalbox (all 4 of them) but Filtrete MERV 12-13 prices increased so much that it doesn't seem like a cost-effective option anymore. It was cheaper for us to buy new HEPA air purifiers (recs via guide from @cleanairstars) than to buy replacement filters for the CR boxes--even with differences in clean air delivery rate (CADR) and HEPA filter cost considerations included.
@crosscutanne @ywlebo correct, which is why $/CADR under required noise levels is so important eg US under 45dBA https://docs.google.com/spreadsheets/d/17j6FZwvqHRFkGoH5996u5JdR7tk4_7fNuTxAK7kc4Fk/edit#gid=1662890714&fvid=1567673968
(Google filterviews must be veiwed on a non-mobile browser)
@ywlebo @cleanairstars It seems to me that prices of commercial and DIY purifiers are getting closer. But as you know it is not just price but the intersection of CADR and dB and price.