Easy how they get away with it: they stop selling cheaper tickets at some point for selected flights. Since the client wants its consultant at work at 10.00 and not at 14.00 am, or a day business trip for meetings should last more than 2 hours around lunch, the consultant or the employee will fly at "peak times" and pay "peak prices". It is not due to flexibility, it is just the SAS way to get captive markets. Tourists don't need to go to HEL if the price is 8500 SEK, business people usually still need to go to HEL whatever the price...

And for the business upgrade, it can be a very good value! Swiss charges 75 EUR per direction, which is too much for direct flights but is very reasonable for connecting flights: quiet cabin with free middle seat, something to eat and drink, fast track in Zurich airport, lounge access... but especially biz class points! BMI charges 12 GBP for 1000 miles, 4 short LX segments in J bring 4800 points (and qualifying ones!), that is worth 70 EUR more or less! and 4500 points, it is what you need for a star alliance direct one way C class award within Europe, in addition to 60 EUR cash and 30 EUR taxes.

LX business upgrade is a very good deal and well worth the money, especially if posting to BMI. SAS discounted biz for direct flights are much less worth the money.