TBH, those vendors sound seriously sketchy absent some credible explanation for why they think they need to charge more for a wedding.

If a vendor who supplies kids' entertainment rental (like those blow-up house things) tried to charge more for their services at a wedding than at a birthday party, I'd think they were trying to gouge. Flowers, something I know very little about, I could understand being treated differently for a wedding than other events, but I'd be interested in why.