= form_for @user, :html => { :class => 'form-horizontal' } do |f|
  .control-group
    = f.label :name, :class => 'control-label'
    .controls
      = f.text_field :name, :class => 'text_field', :required => true
  .control-group
    = f.label :email, :class => 'control-label'
    .controls
      = f.email_field :email, :class => 'email_field'
  .control-group
    = f.label :balance, :class => 'control-label'
    .controls
      = f.number_field :balance, :class => 'number_field'
  .form-actions
    = f.submit nil, :class => 'btn btn-primary'
    = link_to t('.cancel', :default => t("helpers.links.cancel")), users_path, :class => 'btn'

= form_for @user, :html => { :class => 'form-horizontal' } do |f|
  .control-group
    = f.label :name, :class => 'control-label'
    .controls
      = f.text_field :name, :class => 'text_field', :required => true
  .control-group
    = f.label :email, :class => 'control-label'
    .controls
      = f.email_field :email, :class => 'email_field'
  .control-group
    = f.label :balance, :class => 'control-label'
    .controls
      .input-prepend
        %span.add-on €
        = f.number_field :balance, :class => 'number_field'
  .form-actions
    = f.submit nil, :class => 'btn btn-primary'
    = link_to t('.cancel', :default => t("helpers.links.cancel")), users_path, :class => 'btn'

Prepend € sign to balance input field
Prepend € sign to balance input field
