You are right about  latest Telerik version (2012.2) you have to supply now validate.js.
My posts  are not valid for the new telerik version. You can leave validate as is at <head>
But your admin culture problem is still here.
All the steps to fix it

new nopcommerce installation
http://nopcommerce.codeplex.com/SourceControl/changeset/12348f2e706f
download  german langage xml file (has reverse numeric decimal seperator) and install it

step 1
go to https://github.com/jquery/globalize download zip file
copy everything inside lib directory to your administstration/scripts/ as is

step 2 _AdminLayout.cshtml

@using System.Threading;
---
<script src='@Url.Content("~/Administration/Scripts/globalize.js")' type="text/javascript"></script>
<script src='@Url.Content("~/Administration/Scripts/cultures/globalize.culture." + Thread.CurrentThread.CurrentCulture.Name + ".js")' type="text/javascript"></script>
</head>
----------------------
@(Html.Telerik().ScriptRegistrar()
              .Globalization(true)
            .jQuery(false)
            .jQueryValidation(false)
                    )
--------------------      
      <script type="text/javascript">
      $(document).ready(function () {
          $.validator.methods.number = function (value, element) { return this.optional(element) || !isNaN(Globalize.parseFloat(value)); }
          $(function () {
              Globalize.culture('@(Thread.CurrentThread.CurrentCulture.Name)');
          });
      });
</script>
</body>
----------------------------------
step 3 global.asax delete
if (webHelper.GetThisPageUrl(false).StartsWith(string.Format("{0}admin", webHelper.GetStoreLocation()),
                StringComparison.InvariantCultureIgnoreCase))
            {
                //admin area

                //always set culture to 'en-US'
                //we set culture of admin area to 'en-US' because current implementation of Telerik grid
                //doesn't work well in other cultures
                //e.g., editing decimal value in russian culture
                var culture = new CultureInfo("en-US");
                Thread.CurrentThread.CurrentCulture = culture;
                Thread.CurrentThread.CurrentUICulture = culture;
            }
           else
           {
----leave only that part
        }

step 4 bulkedit.cshtml
change
   columns.Bound(pv => pv.Price).Width(100);
to

        columns.Bound(pv => pv.Price).Format("{0:n}").Width(100);


thats all
Of course you have work to do with  hard-wired currency symbols $
----------
The only way to duplicate behavior of  original post is after you finish above steps is  to delete   .Globalization(true)  
(probably just added russian  language at global.asax or other changes)