- At 50 euros/month spending and 10 cents CPC that's 500 clicks/month or 5 sales
- at 200 euros/month that's 2000 clicks or 20 sales
These are simple projections which can reflect and maybe more investment could lead to more sales.
At 200/month (in euros) and 20 sales with price/product at around 12 euros (after deduction of various fees) hardly any profit is left.
It's around 100% ROI with no profit.
Best way to test? try increasing or dropping adwords spending.
+ Find out where this direct traffic comes from and invest in that!