The cost of Google Ads is determined by whether you set a monthly or daily budget, whichever way you want to see it.
Although it is said that there is no minimum investment requirement, certainly if you have a very low budget and your competitors double or triple that budget, obviously they will receive double or triple the opportunities than you to sell to prospects who come to ask.
The cost of a click or a call can vary, among other things, depending on the products and services being advertised, the budget of your competitors who are paying for the keywords, and the time slot in which you advertise. Take into account that if you want to advertise in the United States or Europe, the cost per click is higher than, for example, in Latin American countries.