Good data. suggestive if not definitive. Pal Zarandy at Rewheel offers four years of data comparing 8 European companies. I believe at least 10-15% relative increase is highly likely.
His conclusion: Gigabyte prices in 4 to 3 consolidated German and Austrian markets have fallen considerably behind the Netherlands and other 4-MNO European markets.
Compared to a control group of six countries with four primary operators, German and Austrian prices almost doubled. (Denmark, France, Italy, Poland, Sweden, UK.) Austria went from 30% less expensive than the control group to 74% more. Germany went from 60% more expensive to almost triple the control group.