Dear Sarah58
To actually answer your question ...
I think that seems reasonable. Branded school uniform can be so very expensive - having had 4 children over an 8 year span, I was relieved when uniform buying became significantly cheaper due to more relaxed rules about items bearing a particular logo.
It looks like the uniform the HT is proposing bridges the gap nicely.
As a teacher, I feel school uniform is important - it can be a great leveller and instils a sense of belonging and smartness, but it doesn't have to break the bank. There are also safety issues involved, especially with students who try to bend the rules with trendy footwear that is not fit for the school environment.