One filter is good for 1400 gallons at $30.
A pair of Berkey black filters - even better than the white ceramic ones - are about $100 and will filter 6000 gallons.
To filter the same amount of water you would need more than 4 of the others costing $120.
Better VALUE.
Do the same setup with the buckets and the black Berkey filters will end up costing less in the long run.
A pair of white ceramic Berkey filters are about $60 for the same 6000 gallons so filtering the same amount of water with the Berkey system would cost HALF as much as these at cheaper than dirt.
Spend your savings on a nice stainless steel housing that won't leach anything into the water and will last forever - HEY!!!- Berkey has some of those too ........

Another 'cheap' water filter...
Materials needed...
55 gal. drum(metal or plastic...don't really matter.)
At least a 4 ft. step ladder.
Enough 2 X 4s to build a stand at least 3 feet high for the drum to set on.
1 water faucet with the accompanying accounterments to secure it into the drum so it doesn't leak.
Saw, hammer, nails...or screws and screwdriver.
Goodly supply of sand straw, and charcoal.
Several old bath towels or bed sheets.
And, lastly, no less than 2 buckets that will hold at least a gallon of water.

Build your stand and brace it up good. But be sure to leave a space on the outside 'face' so a bucket can easily be slid under the drum and out.

Punch a hole in the center of the bottom of the drum and fasten the water faucet into it. Being careful to not damage the faucet, set the drum on the stand.

Now cover the bottom with one of the old bath towels or a couple layers of the bed sheet...don't use the whole sheet.

Now, being careful to not let any get beneath the cloth, lay in a layer of straw (about 6 inches thick). Next a layer of ground down charcoal (about 4inches thick). Now a layer of sand (again, about 4 inches thick.) Repeat with a layer of straw, the charcoal, and then the sand until the drum is within about 6 inches of the top edge of the drum, forming the last several layers into a sort of shallow cone. Be sure that the last layer is one of straw. The filter is now finished.

Using one of the gallon buckets, obtain and 'GENTLY' pour the 'dirty' water into the middle of the filtering straw. Place the other bucket underneath the drum and open the water faucet. Keep pouring the dirty water into the drum lettin it soak into the filtering material between each filling. You should only do about 4 or 5 buckets worth at a time, though it depends on the number of people yopu need to supply with water. You will also need a large container to hold all the water that comes out the faucet in the bottom, too. This filtering system is for 6 to 12 people, and will need to be redone about every month(IIRC). A 5 gallon bucket can be set up very similar that would do well for a single person except that it would need to be reworked a lot more often.

It's been a while since I studied up on this and I can't recall all the 'figgers' but that'll definately get you clean drinking water. Once the water has drained through this filtering system, you can treat it with the bleach. Some say to do that as an integral part of the system, but I don't really see the need.

Anyway, there's you another water filtering system. It worked well for the Folks in the back country back in the mid 1800s, so it should still work for us...tomorrow.