Assuming you mean a bespoke trust fund then it would depend on the complexity of the trust and also how complicated your will is. However, having said that £2,100 sounds like an awful lot to pay. Suggest you get one or two other solicitors to give you a quote but they'll need to know the type of trust.
Whatever you do think very hard before you appoint a solicitor as either executor or trustee as it can be very expensive. If you can make family members or good friends executors and trustees - they can always employ solicitors if there is a particularly tricky problem they need to deal with.