Instagram impressions are the cheapest thing on this page by a wide margin, which makes them the sensible way to test whether a provider delivers at all before spending real money with them. They are also the most forgiving: nobody audits a view count, they do not drop the way profile-level numbers do, and the failure mode is that nothing arrives rather than that something arrives and then vanishes.
Instagram is the most competitive and most scrutinised market in this category, which means both the best supply and the worst. Its own detection has been running longest, its periodic purges remove bought followers in visible batches, and the engagement ratio on a profile is the first thing any brand checks before a partnership. The practical consequence is that Instagram is the platform where proportion matters most: a follower count far ahead of the likes underneath it is read as bought by humans long before any algorithm gets involved.
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 post 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.