This is a very open ended question as there’s a lot of variance to consider. Generally speaking the newer the unit, the cheaper it will be to run. If your system is 10 years old or more, then it could cost twice as much as the modern equivalent.
While you can find washable pre-filters in the majority of modern air purifiers, other filters are rarely washable.
Washable Carbon Filters – Sometimes, you will come across an air purifier with a reusable carbon filter. This is a good option for households or other spaces that are exposed to smoke and other strong odors. Carbon filters are also great at dealing with volatile organic compoundv (VOCs), chemicals, and various odors, so washing them every couple of weeks is the best way to tackle unpleasant smells. Eventually, you will need to replace the carbon filter as it does wear out, but being able to wash and clean it, will prolong the lifespan considerably.
Washable HEPA Filters – Some manufacturers offer washable HEPA filters. However, these filters are rarely the top grade of HEPA filter and usually inferior in quality. Washing a HEPA filter will most likely destroy the delicate arrangement of the fibers, which allow the filter to deal with 99.97% of particles 0.3 microns in diameter. The maximum level of cleaning a real HEPA filter can usually endure is delicate vacuuming.
If you see an air purifier with a washable HEPA filter, it’s probably not a Pure or True HEPA but a HEPA 4 filter, which is virtually useless for small particles. Even if after cleaning it, the filter looks intact from the outside, it is likely to be ruined on the inside. Eventually, you would still need to replace this type of filter.