Let's take a marine water filter that gets rid on most of the "nasties" that make you sick, the Seagull is stainless and quite popular with cruisers...
It really is a pretty good water filter and it will keep your water potable and safe which after all is the whole point. It is stainless steel and well built but it also costs $500... Made worse as the filters need replacing on a regular basis (around 1000 gallons of use best case scenario) and the filters are also not cheap. for those who don't have a pressure system on their boat and use foot or hand pumps (a very sensible approach) the Seagull won't work as it needs more pressure than most manual pumps provide which becomes somewhat problematic.On the other hand the Sawyer, which is coming from the backpacking world, does the same job getting the nasty critters out of your water and in comparison to the Seagull at less than $50 it has to have some serious drawbacks or so one would think. Fact is, as much as I look, I find the Sawyer is way ahead of the Seagull any way you can look at it.
While not built of stainless (it's plastic) it is just as Marine environment friendly as the Seagull. It does not need replacement filters as the unit is guaranteed for one million gallons of throughput before you need to replace it. You may need to clean the filter from time to time but this is a simple two minute affair and as the whole Sawyer unit is cheaper than the Seagull replacement filters, it is pretty easy to do the math...
What is even better is that low pressure systems and those of us using hand or foot pumps are covered as it does not require more pressure than can be provided by your basic Whale foot pump which is all kinds of good.
So here's the test... Do you spend $500 or $50 for something that does more or less the exact same thing? Just how important is the word "MARINE"?