I run an event production company in Hong Kong. One of the event types we do are weddings. Celebrants often ask us to provide a band to play jazz during dinner and dance music thereafter. Unfortunately, very few people understand that hiring a live band is not cheap. (I reckon this is because most people have never tried to hire a band before.)
Hiring a good, professional band in HK will cost HK$30,000 and up. Sounds expensive! I know. Here's why: each band member needs to get paid. They perform for a living, not as a hobby and musicians have to eat and pay rent just like everyone else.
They also need to rehearse prior to the wedding performance, especially if the bride or groom have any special requests. This takes time and requires the band to rent a studio. These two points might seem fairly obvious, but the final cost is overlooked by most people...
You have to hire a sound system and musical instruments specifically for a live band. Keyboard, drum kit, amplifiers, mixing board, audio engineers, stage monitors etc. are all essential to a live band performance. And "no", the venue does not provide these. All of this kit must be transported to the venue, set up, tested, dismantled and taken back to the warehouse. No sound system, no music.
So, a live band is a great idea that will make a wedding banquet more fun. But you've got to set aside the budget for it. I am happy to answer questions about this or anything else related to live event production.
Dave
Chunky Onion