Investing too little can lead to limited coverage throughout the day, running out of budget before the day is over. This means that your ads will not be visible for the entire day, reducing sales opportunities and potentially leaving room for competitors. In practice we entice customers to buy, and when they decide to do so, they don't find us, they find our competitor.
Setting a daily budget for a Google Shopping campaign requires a careful analysis of your e-commerce's annual revenue and the percentage of advertising investment typical in your industry. Here is a table summarizing the average percentages of turnover allocated to advertising for various business sectors and an estimate of the recommended daily budget, based on a hypothetical annual turnover of €500,000.