Correct. I go a lot further, with multicoated (doublesided) filters, as required and a lens hood. I am not averse to spending $1,000 on a single filter. I don't take shortcuts.
Too many people put a $5.00 bottle end filter on a $4,000 lens and think all will be well and good. The truth is that a poor quality filter compromises the optical integrity of the lens, resulting in flare, loss of contrast and in the worst of cases, loss of clarity. Part of the problem is that cheap filters are promoted by dealers at POS, at the time of sale. They ought to be convincing the person on the other side of the counter that he/she is paying a lot of money for a lot of lens for a good reason: that of technical refinement that is far, far removed from the emotive, nostalgic "high quality" lenses of 30 to 50 years ago, and that the filter must be equal to the quality of the lens, but in no way compromise it. But in this digital, fast-sell age, it seems making the sale is more important than building quality on quality when accessorising, filters particularly.