It deoends on area but for a general pub I think you are looking at around £200 - £300
Larger pubs / venues £300 - £500
Functions can go from £300 - £1,000s +
Weddings are usually more £700+
The thing to bear in mind with pubs is that it is tough times for them at the moment so price will be more of a "business decision" than a "quality" decision
A crap band that brings in loads of "fans" that drink all night will be better for a pub than a really tight band that doesn't bring anyone
If you can come up with some clever marketing ideas - "we will promote the night ourselves by..." you may give the venue more confidence and you can up the price a little
The other model is for the pub to sell tickets for the event where the band gets the "on the door" money and the pub makes on the drinks - I dont like this model as it limits the crowd so neither party really wins
If you are starting out I would suggest pitching at around £150 - £200 as an "introductory offer" and then you can negotiate for a string of gigs - e.g. "our normal price is ####, but if you commit to 4 bookings we will do them for ####"
You could even offer a "freebie" to try it out if the venue was undecided but it looks line you have already made the sale!
Are these the kind of figures you were thinking?
Ultimately you need to decide what makes it worth it
I still really enjoy playing live and as long as I get a few pints of Fosters and a kebab anything else is a bonus!!!
Finally, if yiu ever get challenged on price you can always use the following:
"Gets a quote for 5 plumbers to turn up from 7pm 'till midnight and we will charge half of that!!!"