So it's been a while since I've sold advertising spots, recently got contacted by a fairly well known company in that niche for one of my side projects that is interested in advertising. I haven't followed up yet but want to have an idea beforehand of what would be a fair rate to charge them. I'm not sure if they'll want to go with a CPM route or a fixed ad spot per month. Regardless, what is a good factor to determine what to charge? Their product is a subscription service that costs under $20 a month. Like assuming traffic is say 20K UV per month. Thanks for any insight.