Snapchat followers attach to your profile permanently, which makes them the one purchase on this list where retention is the whole question. Anyone can deliver a number for a day. What matters is what is still there in a month, and the honest position is that this is measured by almost nobody — including, at the moment, us. Ask a seller directly what their refill window is, whether it is automatic or a support ticket, and what happens if the drop lands on day thirty-one.
Snapchat is the awkward one, because most of its numbers are not public. There is no visible follower count on a personal profile, Story views are visible only to you, and the Snapchat+ subscriber counter is the closest thing to a public metric there is. That means most of what is bought here is invisible to anyone but the account holder, which removes the social-proof rationale entirely. Buy Snapchat metrics for the algorithmic effect if you believe in it; do not buy them expecting anyone else to see the number.
Beyond the metric itself, the same four things separate a working order from a wasted one, and none of them are visible from a landing page. First: whether the seller asks for your password. No legitimate provider in this category needs one — a public username or a profile link is all the work requires — and a request for a login is the end of the conversation, not something to weigh against a lower price.
Second: whether the price you are quoted is the price you pay. Retail sellers here quote packages and panels quote a rate per 1,000, and the gap between them once you normalise is routinely fiftyfold. Every figure on this page has been converted to the same per-1,000 unit for exactly that reason.
Third: what the refill promise actually says. "Refill guarantee" is a marketing phrase until you read the window, the trigger and the process. Thirty days, automatic, no receipt required is a real guarantee. Thirty days, on request, subject to review is a support ticket you will probably not bother to file. Fourth: whether the seller has been trading long enough to still exist when you need the fourth one. Domain age is on every provider's page here, and it is the cheapest signal in the category.