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Those are the average, you can find them on splintercards.com. Long-term, your rewards should be extremely close to those numbers. Keep in mind that a single Gold Legendary would be close to 100$ :)

Yeah, I found it few minutes after I wrote that :)
Sadly I'm still nowhere near that average. My most valuable card is gold Venari Heatsmith (worth like 50c). Got 3 epics and that's all worth mentioning.
But hey, I'm not giving up, I'm just saying its a long road ahead. I just need to relax and enjoy the ride