Is your budget distributed throughout the day, do you get clicks at all hours or is your budget used up at the time you get the orders?
If you set a daily budget of $100 that budget will be used up as fast as it can by Google during the day, they don’t really have a system for distributing it during the day, and it might just be that you get a conversion before the budget is used up.
If that is not the case, I think it might be coincidence.
6 conversions in 1200 visitors is quite few, if you want to try it out we have an app that automates both Google Ads & Google Shopping. We create Ads, publish feeds, translate into native language and have an AI optimization based on probability. It’s 30-days free trial so you can see the results before you have to pay. (https://apps.shopify.com/amanda-automatic-google-ads)
If you want to continue to do it yourself, I would recommend that you focus on analysing where you are getting those conversions. Are there common things you can find that drives a conversion, and if so, can you raise the bid for those things? Paying 6-cents / click isn’t necessary better than paying 30-cents / click if you get more conversions for your ad-spend.
Start with the simplest
Best of luck
Your data sample is to small to make any judgement calls on what is going on. Getting sales is good and if this is Google Shopping, then the CPCs sound good. You need to run your ads longer and get more sales before you know anything. Otherwise, you are just making guesses and assuming to much.