https://il2sturmovik.com/ will have sent existing accounts discount codes, and will be sending to new accounts on a daily basis starting Monday.
The codes give 50% off for Battle of Bodenplatte and Flying Circus, and 75% off for the rest of the finished products.
That's $40 for Flying Circus, $25 for BoBP standard edition and $12.5 for the other standard editions. Good value for you money, possible excluding Flying Circus at this time.
Edit: Should add that as long as you have Stalingrad on steam, they integrate just fine with the steam version.