If it's really expensive direct to Scotland, you could try American Airlines to London and pick up a local carrier to Scotland.  Depending on how far in advance you book, you can get tickets on the discount carriers for $2 plus fees, which works out to about $60 per ticket.  If you do though, read their luggage restrictions VERY CAREFULLY.  For example, Ryanair lets each passenger carry a toothbrush and comb, then charges about $50/lb for checked baggage.
Ok that's a small exaggeration, but you get the idea.