Care to link to a major equity exchange's product page and/or sec declaration that details exactly how this works (ie, criteria for getting "first dibs", what that actually means etc)?
Or are you talking about exchange hosting, where you get lower latency if you pay more to colocate?
Every exchange gives "good standing market participants" aka HFT market makers first dibs on orders. If a gallon of milk goes on sale and I'm waiting in line with a market maker I will never make the sale, it'll go the the HFT firm every time.