£10 (or the US equivalent) doesn't sound like a whole lot of money. I'd be willing to pay that amount for performers I really want to hear - BUT it's still a significant amount of money. I go to a lot of concerts for what one might consider "charity" reasons - I want to support the venue and ensure it has a full house, I feel it's my duty as a member of the local folk community, it's a new performer and I want to see if he/she is good or not, it's a not-so-good performer and I don't want his/her performance to be a flop, etc.
Some performers are a sure bet, and they're worth £10 - I'm sure Vin Garbutt is one of these. I'd hate to see £10 become the standard price, because it shuts out many performers who may not be considered to be worth £10.

$20 is becoming a fairly common price for folk house concerts in the U.S., and that's a bit steep. I find the price is high enough to discourage me from attending concerts I'm not sure I'll enjoy. $50 or more is now the price for well-known performers in big venues, and I'm rarely willing to pay that. I still regret missing my first chance to see Doc Watson a couple years ago, but the cheapest ticket was $58, and I had to drive an hour each way to get to the concert.

-Joe-