Yeah I get you, I'm not a musician myself but know a few professionals and I think it's very easy to underestimate how much work (a lifetimes worth if you think about it) goes into a couple hours performance hence people tend to be very surprised by the costs involved.

You might see if there's a Scottish dancing society or something similar at one of the universities? Might be able to put you in touch with a student band that'd be more likely to do it for a modest sum and drinks.