If you use another language then english you cant delete a added price from the grid.
The error is on line 44
<asp:TemplateField HeaderText="<% $NopResources:Admin.ProductPricesByCustomerRole.Delete %>"
HeaderStyle-HorizontalAlign="Center" ItemStyle-Width="15%" ItemStyle-HorizontalAlign="Center">
<ItemTemplate>
<asp:Button ID="btnDelete" runat="server" CssClass="adminButton"
Text="Delete" CausesValidation="false" CommandName="<% $NopResources:Admin.ProductPricesByCustomerRole.Delete %>"
ToolTip="<% $NopResources:Admin.ProductPricesByCustomerRole.Delete.Tooltip %>" />
</ItemTemplate>
</asp:TemplateField>
Should be:
<asp:TemplateField HeaderText="<% $NopResources:Admin.ProductPricesByCustomerRole.Delete %>"
HeaderStyle-HorizontalAlign="Center" ItemStyle-Width="15%" ItemStyle-HorizontalAlign="Center">
<ItemTemplate>
<asp:Button ID="btnDelete" runat="server" CssClass="adminButton"
Text="<% $NopResources:Admin.ProductPricesByCustomerRole.Delete %>" CausesValidation="false" CommandName="Delete"
ToolTip="<% $NopResources:Admin.ProductPricesByCustomerRole.Delete.Tooltip %>" />
</ItemTemplate>
</asp:TemplateField>
