Well,it’s the same logic that fb ads have for learning phase : you need a number of conversions so google can tell who your customers are. It’s difficult to put a budget on it from the start. Some of my clients get conversions for 1$,others for 10$.
Be aware that the pricing of your product is much more important in google than in fb : your products (and competitors) are listed in font of the searcher with prices. Imagine you search for an iphone and you get listings;1000$,800$ and 1200$. SAME iphone. I’d say you would click the 800$ one.
Start a campaign with maximise conversion objective, put 100$ on it and see how it goes for 2 weeks.