I'm stuck on CSV generation based on a list of folders

Good Day Fellow Techies ! 

First time poster here but I've been benefitting from you guys for few years already 🙂

I'm trying to generate a CSV file based on a folder structure as shown below for a urgent requirement. Each folder has multiple PST files in them (some has 1 and some may have even 4or 5 in the real scenario). I basically want to generate a CSV with file path for each PST file with the respective username. 

Folder structure: C:\Tools\PSTTest\PST

Files: in each folder/s:

Expected result be like this: but unfortunately I struggled to fix it for few hours now 

Issues:

1. in my current PS Script, its all gets mixed (Other's entries also falls under Bill.Gates and repeats across the others as well so its all messy)

2. and also generates an extra .PST at the end of the every item. 

Current output CSV: 

My Script: 

$MigrationList = import-csv "C:\Tools\PSTTest\CSV\SourceUserList.csv"
$ContosoUsers = $MigrationList.SamAccountName | sort -Unique

$root_folders = dir "C:\Tools\PSTTest\PST" -Directory | select fullname
$user_pst_list = @()
$user_pst_list_folder = @()

$Date = Get-Date -Format yyyy-MM-dd

foreach($user in $ContosoUsers)
{
    $Contoso = $user

    foreach($folder in $root_folders)
    {
        $folder_path = $folder.fullname
        $user_pst = dir "$folder_path\" -Recurse -Include *.pst -ErrorAction SilentlyContinue | select @{label="Contoso";expression={$Contoso}},fullname,name,@{label="SizeKB";expression={($_.length) / 1024}},@{label="SizeMB";expression={[math]::Round((($_.length) / 1048576),2)}} | ?{$_.SizeKB -gt 265}
        if($user_pst)
        {
            $user_pst_path = $user_pst.fullname
            $user_pst_list += $user_pst
            $user_pst_folder = get-item "$folder_path\$Contoso" -ErrorAction SilentlyContinue | select @{label="Contoso";expression={$Contoso}},fullname

            if($user_pst_folder)
            {
                $user_pst_list_folder += $user_pst_folder
            }
        }
    }
}

$user_pst_list | export-csv "C:\Tools\PSTTest\CSV\pst_list_$date.csv" -nti

If you can help out showing me the issue in this script I would be very grateful ! Thank you very much !

-Kevin