There are plenty of cheap filters available in the Hot Tub market, sometimes 30% or even 50% cheaper.
These filters are cheaper because they use an alternative, cheaper media (the pleats).
These cheaper filters:
1) Cannot be washed and re-used
2) Will become 'blocked' and lose porosity very quickly. This will reuslt in a drop in water pressure coming from the jets and continual 'FLOW" error messages on your control panel because there is insufficient water flowing through the circulation pump. This will then result in a drop in heat and possible ceasure of the pump. A costly exercise.
3) Can collapse and become unusuable within 6 months. So you will need 4 filters instead of 1! Thus the cheap filters are probably TWICE as expensive.
4) Can release Phosphates from the bonding elements within the material. Phosphates are EXACTLY what the filter is supposed to be preventing. Phosphates are vital food for algae and bacteria, thus your spa water could become a health hazard and green in colour. An indicator of Phosphate is a Yellow Filter (see below)