As for my rates I have 3 different plans and a system of discounts (here http://www.learnrussianinmoscow.com/index/fees/0-2). As for Skype lessons, they are cheaper: 1 academic hour (=45 min) = 750 RUB (about $24). So one lesson of 90 minutes = 1 500 RUB. Minimum 8 lessons per month.