As an upgraded member you are guaranteed 3 extra ads per day and you will be paid $0.01 for each one of them. This is $10.95 per year if you never miss an ad but the upgrade will cost you $17 per year or $15 per year if you buy 2 years at once. The one ad for $0.01 you are guaranteed as a not upgraded member will stay with you.
$10.95 per year means $0.9125 per month while the monthly cost of the membership is $1.4167 or $1.25 if you buy 2 years at once.