Do you need it for the FTL status (segment run till 35)? LOT promolot domestic fares should be the easiest, with around 75 PLN cost per segment.
You can probably do 4 segments a day, so you'll be done in a week.

If you want to do it fairly quick and comfortable, you'd have to splurge for some premium fares (with some positioning flight added on) - that would be at least twice as expensive.

Anyway, if you only did 13 segments/less then 7k miles this year it doesn't sound like it's worth the investment in status for you. If you do have plans for more travel in 2011, maybe get the status miles next year and then you'll have FTL status till Feb 2014 (rather then 2013 if you re-qualify this year)?