Cost per successful request is the only number that matters
Advertised price per gigabyte is close to meaningless on its own. In our testing the cheapest provider by GB was not the cheapest per successfully retrieved page on difficult targets, because failed requests still consume bandwidth and engineering time. Run a paid trial against your actual targets and calculate cost per success. Providers will happily quote per GB because it flatters them.
Match the proxy type to the target
Datacentre IPs are cheap, fast and easily identified — fine for undefended targets and useless against anything with real protection. Residential IPs come from consumer connections and pass most checks at ten to twenty times the price. Mobile IPs are the most trusted and the most expensive. Most teams overpay by using residential where datacentre would work; test the cheap option first and escalate only where it fails.
Ask where the IPs come from
Residential proxy supply chains vary from clearly consented — users paid or given a free product in exchange — to opaque bundling inside free apps where consent is buried in a EULA. This is a real ethical and legal question, and increasingly a procurement one. Providers with published compliance frameworks and named consent mechanisms are worth a premium over those who will not explain their sourcing.
Know your legal position before you scale
Scraping publicly available data is broadly lawful in many jurisdictions but the picture is genuinely complicated, and it varies by what you collect, where you are and what the site's terms say. Personal data brings GDPR obligations regardless of whether the page was public. Get advice before building a business on it rather than after receiving a letter.