Don't buy amway/atmosphere, half of the money you paying are just going into the MLM salesman's pocket, especially when you need to buy their exclusive filters in future. Their salesman like to boast about the faster air flow and "better than HEPA" filter rate, which is purely salestalk. The real professionals in the air cleaning business would ask you about coverage/volume, which mean if you have a big house, it is better that you install multiple "normal" air purifiers than 1 super-expensive one.

For me, as long as the air purifier has the HEPA filter and the replacement filters is reasonable priced and widely available through retail channels then it is good enough. Anyway there are a few classes under HEPA, most of the air purifiers under RM1K has the lowest class H10 which is only 85% against <0.3 micron particle.