Are you curious because you want to compare others' numbers to yours? That would be pretty useless. There's so many things affecting conversion rate.
But to satisfy your curiosity, I'll give you some numbers. I manage PPC campaigns for these clients, all US traffic.
Client A: about 2.3%, some categories higher and I've seen close to 10% in some categories at certain times of year. More competition in this area and conversions are currently lower than they were when started campaign five years ago. Hundreds of items ranging from $20 to $75.
Client B: Thousands of items selling $1 to a few at $1500. I don't promote those under $20. Rates at around 2% as well but near 3% this month and close to 4% last week, his best ever. This after telling him to change his pages to increase conversions. He finally started doing it this month and look at the results.
Client C: Just starting on his campaign but his conversion rate was 5% last year. Basically same product selling in different sizes ranging from $15 to low $100s. Hoping to increase conversion to 8% or more based on account analysis and optimization.
Other clients over the years with wide range of conversion rates in many verticals. One was over 10% consistently.