The wording makes it sound like you only tested your filtered water. Seems like you'd want to test both the pre-filtered and post-filtered water to really know if your filters are "very effective."
$400 seems quite high. There are much cheaper tests available, such as the National Testing Labs City Check test ($126 + return shipping) at https://www.purewaterproducts.com/watercheck/
Essentially, Berkey was created to resell British Berkenfeld / Doulton filters in the US. They simply tweaked the brand name Berkenfeld into Berkey and began US distribution. Doulton has a rich history, and is a very legitimate brand. They invented ceramic filters in Victorian times. Berkenfeld was a German competitor that was transferred to British hands after WWI.
Once Berkey started selling well, they began sourcing some filter candles in China. These are no longer Berkenfeld / Doulton. They don't look similar.
In the mean time the only way I've been able to think of to reduce potential contaminated water is to vary my sources.
[1] https://www.eastbaytimes.com/2019/05/03/oakland-unified-lead...
We used to live somewhere (in the US, to be clear) that, if you made iced tea with tap water, you could smell it as you brought it to your mouth. The water, I mean, not the tea. Smelled kinda sulfurous, and otherwise just off-putting. You could tell if a restaurant didn't filter their water because you could smell it in the cup, from a good foot away (luckily, most filtered it). This despite bathing and washing clothes in it and therefore probably being less sensitive to the odor than someone from out of town would be.
Needless to say it tasted terrible. We didn't even cook with that stuff. Cheap gallon jugs of filtered water for cooking.
Well water I assume?
I used to RO my water with a 5 stage filter. Lately I bypass the last two stages and just do one stage of 5micron sediment and 2 stages of charcoal block.
Chlorine smell is gone, taste is great, and the filters in bulk cost $1.50 each for the sediment and $3.00 each for the charcoal. I change the sediment monthly (it gets quite discolored) and the charcoal every quarter. So $42/year in filters.
My wife had a pretty bad bottled water habit before I filtered, so it’s a huge cost saver. We fill water bottles several times a day for us and the kids, so probably ~1,000 gallons a year? Plus it also goes in the coffee machine, and for cooking.