When I put quarterbacks in tiers I try to simplify it. Keep in mind, I am considering these QBs in their prime. Tier 1 QBs being reserved for the best. Brees, Brady, Mahomes types.
Tier two being very good QBs, but just don't have enough to be elite. They can play elite on occasion, but are not consistent enough to be considered elite. You may have just as many people argue for them being elite as those that say they aren't. QBs, like Romo, Stafford at one point, Boomer Esiason, Rivers, Watson, guys like that.
Tier 3 is pretty much everyone else that doesn't outright suck to being a decent QB. Bridgewater, Cousins, the guy from the 49ers I can't spell, Tannehill, Carr. These are the guys that need a really good supporting cast.
Tier 4 is....need I explain?
That's my simplified way to rank them. The QBs in the first two are usually going to get the big contracts. Some of the tier 3 guys will get them, but only if their team has success.