Here is a good article on account-level Quality Score, specifically discussing the costs of migrating to a new account (with some speculation):
If you’ve inherited a “dog” account, it could be a long, long time (like maybe forever) before minimum bids on a poor account get down to sustainable levels. It’s as if Google starts out assuming you’re an idiot, but then you have to go and prove it by ringing up piles of untargeted clicks. Now they know you suck.
So if you inherit this puppy, the long struggle to right the ship may wear you down, and the client’s budget may be exhausted if you aren’t first.
But why should you have to suffer indefinitely?
Google reps may tell you in specific cases that even taking into account the time it takes to build up good signals for strong account-wide quality, it might still be better to dump the old account in favor of a fresh, new one.
I’ll repeat that takeaway to be clear. You may save yourself weeks or months of pain by huddling with an AdWords rep who can frankly advise you on whether you should keep an existing account (if its Quality Score history is mediocre to good) or whether you should delete it entirely and start a fresh one (if that overall Quality Score is truly stinky).
…Reminder: you need to adopt a staged buildout strategy for new accounts in AdWords these days. Start with broad and experimental types of targeting and you’ll be fighting the Quality Score gods. Build up a strong account history with a tightly targeted (smaller but more beautiful) campaign, and you should get the green light to ramp up sooner.
Either way, though, unless it’s a very conventional e-commerce account, it takes time to get Great Quality Scores. Established accounts that are already doing well work differently – initial quality on new keywords can come in “Great.” But on new accounts, it’s harder.
…In less mature markets, we continue to see the Quality Score bar set less strictly. But what is particularly pesky, especially in the US where keyword auctions are already clogged with willing participants, is how sensitive and smart the predictive keyword relevancy algorithm is.
…Again, to generalize is difficult, but in today’s environment, to the 1-3 month “testing budget” for new accounts, you can probably tack on $5,000 at the low end, and $50,000 at the high end – just to run your account normally, at increased bids to ensure greenlighting (establishing account-wide quality) sometime this decade, or before climate change boils us all stupid, whichever comes first.
…Let’s explore that math. Except if they get very lucky with an extremely conventional ecommerce account, many small firms will now see their “get up and on Google” cost increased maybe sixfold.
…For the big guys – they’re not seeing a 500% increase in ramp-up costs. It’s maybe more like 25% or 30%.