For comparisons sake; Good segment runs cost about 30 euro per segment. That generally means roundtrip flights over short distances from a non-hub to a non-hub airport (4 segments) at just over 100 euro.

In order to get around minimum-stay requirements (to save time you'd generally want to fly back on the same aircraft that you came in with) you can nest two roundtrips (A & B):

Trip A: ABC-DEF (Day 1)
Trip B: DEF-ABC (Day 1)

Trip B: ABC-DEF (Day 2)
Trip A: DEF-ABC (Day 2)

I would recommend to calculate how much money you would spend before doing this though. It is very easy to spend more money this way, than simply buying lounge access as a non-elite...or better yet, simply buying yourself a meal at an airport restaurant. Lounges are nice, but each lounge visit should not be worth more than ~15 euros. Since for that same 15 bucks you can get a better meal elsewhere