Finally applied it properly. Thank you #lexicore
Here is my implementation for the mixed property
{
     type: 'classInfo',
     localName: 'ItemizedForDateType', //<date>
     propertyInfos:[
            {
                type: 'element',
                name: 'priceTextType',
                elementName: 'price',
                typeInfo: 'DOTWXML.PriceFormattedType'
            },
            {
                type: 'element',
                name: 'priceMinSellTextType',
                elementName: 'priceMinimumSelling',
                typeInfo: 'DOTWXML.PriceFormattedType'
            }
    ]
},
{
     type: 'classInfo',
     localName: 'PriceFormattedType',                           
     propertyInfos:[
        {
            type: 'elementRef',
            name: 'charge',
            elementName: 'formatted',
            collection : true,
            mixed: true
        },
     ]
}
And the result of unmarshall is something like the following:
    "itemizedForDateType": [
      {
        "TYPE_NAME": "DOTWXML.ItemizedForDateType",
        "priceTextType": {
          "TYPE_NAME": "DOTWXML.PriceFormattedType",
          "charge": [
            "236.8738",
            {
              "name": {
                "namespaceURI": "",
                "localPart": "formatted",
                "prefix": "",
                "key": "formatted",
                "string": "formatted"
              },
              "value": "236.87"
            }
          ]
        }
      }
    ]
I made a mistake by removing "collection : true" and was getting "{}" after unmarshall. Once I realized the "collection : true" was required, put it in the context and everything unmarshalled properly.