Google ads quality score is a score given by Google to determine how relevant your ads are. Your quality score is based upon click-through rate (CTR), ad relevance & landing page experience. Improving those three metrics will make your quality score improve.
Google AdWords agency pricing can cost anywhere from $500-$5,000 per month to set up & manage your google adwords. An agency setting up your Google AdWords will quote your project commonly based on how much you plan on spending.
While you probably won’t find an average ROAS by the industry for Google Ads, you can look at some data from Google. The average benchmark is 200% a 2:1 ROAS, or an average return of $2 for every $1 spent.