A RTW trip in F should do the trick to maintain your status if you are outside of Germany and need only 100k for SEN requalification. You will however need to do most longhaul trips with LH (where available) to receive the 25% status bonus.

The cost of an FRWSTAR1 ticket should set you back +/- € 7.500, plus the hotels of the 10 day trip, depending on where you start the trip.

If you are starting from zero you will have to do more, as the 25% status bonus only kicks in after obtaining (useless) FTL status.

If you already have some status miles a CRWSTAR1 fare in business class might also do the trick.