I agree with Gamma. If someone buys $18 kit with 10 filters and loves it, he will run out long before more filters can get to him.
An alternative is to put 100 filters in the initial kit plus a coupon code (with a tight deadline) to make the first filter reorder a great deal for the user.
This game will be won with long term filter orders.
Perhaps multiple options can be considered. Perhaps SFIO is already considering this. The $18 option or the $25 option with more filters initially.
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