What rate are covered services billed at before reaching deductible?

In comparing plans, I got stuck on one detail that would help determine which is a better value for our family and I can't seem to find an answer to. In a lower premium/high deductible plan, there have been years where we don't even meet our deductible and end up paying out of pocket for everything. Everyone knows that insurance companies negotiate insanely low rates ($288k billed for a recent surgery and insurance ended up paying about 1/10 of that), far lower than what any surgeon/hospital would accept if paying cash. Before you meet your deductible, are you paying the agreed upon insurance rate (since it's submitted to insurance and the cost is just passed on to you?), cash rate, or something even higher? If it's the former, a high deductible plan may likely be the most cost effective option, if the premium is low enough.