Yes, 300GBP is typical for a tech conference in London. Cost of venues and catering can be astronomical, so even with that ticket price it may be difficult to run a conference.

Some community conferences are half of that (and depend on sponsorships), but OTOH there are also plenty of "serious business" conferences that are 10x more expensive.

The conference would not be possible without the substantial contributions of sponsors, in particular Symmetry Investments. The D Language Foundation does not make a profit off of it. I pay my own expenses to attend, for example.

Is catering a big portion of the ticket price? Surely one can venture outside to nearest starbucks, pret, other-fancy-coffee-shop-5metres-away, and dozens of other eateries? Or the food delivery service apps. I'd be pissed off if shitty non-choice catering was going to eat into the ticket price more than 15gbp. Sponsors pay the booze after usually. So what's left after speakers, token tickets, and venue fees?

The point of the catering isn't just to fill your stomach, it's to have lunch with people who are interested in what you are interested in, ie. to network. If you don't see the point of that, then yeah it's really not going to be worth it for you.

I've been to a few regional conferences so perhaps out of touch, but in those scenarios it's usually either yawn yawn buffet or in most cases a bag with some posh sandwich etc.. in with sponsor logos all over it. I get what you're saying but I can't help but start picturing a table cloth lunch with waiter service as you discuss the merits of the last talk over a fine wine on a table for two/three? perhaps this happens at build? strangeloop?aws:invent? How much of a ticket price is attributed to catering in either scenario?

Aside from keeping the conversations going, keeping lunch on the premises makes it easier to round everyone up after and decreases the likelihood that people are disruptive by streaming in after the post-lunch talk starts. And it's pretty much expected. I would be dismayed if DConf sent me outside for lunch on my own dime.

That seems fine for a London conference, which can cost slightly more than another location due to the desirability of being in London.

London has good air service connections for most of the world, so higher costs running the conference in London is more than offset by lower travel costs by the participants.

It's actually rather cheap, given the venue.