Dim timeDiff As TimeSpan = (TimeSpan.FromDays(2) - TimeSpan.FromDays(1)) ' 1 día de diferencia inicial.
 
MsgBox(timeDiff.Hours)                                 ' Valor:  "0", puesto que es la hora Cero del dia Uno.
MsgBox(timeDiff.Add(TimeSpan.FromHours(1)).Hours)      ' Valor:  "1", puesto que es la hora Uno del dia Uno.
MsgBox(timeDiff.TotalHours)                            ' Valor: "24", puesto que hay 24 horas de diferencia entre día Uno y día Dos.
MsgBox(timeDiff.Add(TimeSpan.FromHours(1)).TotalHours) ' Valor: "25", puesto que le añadí 1 hora a las 24 horas de diferencia.

Public NotInheritable Class DateUtils
 
    ''' <summary>
    ''' Prevents a default instance of the <see cref="DateUtils"/> class from being created.
    ''' </summary>
    <DebuggerNonUserCode>
    Private Sub New()
    End Sub
 
    <DebuggerStepThrough>
    Public Shared Function CalculateMoney(ByVal timeIn As TimeSpan, ByVal timeOut As TimeSpan,
                                          Optional ByVal x1HourMoney As Double = 500.0F,
                                          Optional ByVal x15MinMoneyAfter1Hour As Double = 150.0F) As Double
 
        Dim timeDiff As TimeSpan = (timeOut - timeIn)
 
        Select Case (timeDiff.TotalMinutes)
 
            Case Is <= 0.0R
                Return 0.0R
 
            Case Is <= 60.0R
                Return (x1HourMoney)
 
            Case Else
                Dim fractions As Double = Math.Ceiling((timeDiff.TotalMinutes - 60.0R) / 15.0R)
                Dim supplement As Double = (fractions * x15MinMoneyAfter1Hour)
                Return (x1HourMoney + supplement)
 
        End Select
 
    End Function
 
    <DebuggerStepThrough>
    Public Shared Function CalculateMoney(ByVal dateIn As Date, ByVal dateOut As Date,
                                          Optional ByVal x1HourMoney As Double = 500.0F,
                                          Optional ByVal x15MinMoneyAfter1Hour As Double = 150.0F) As Double
 
        Return DateUtils.CalculateMoney(TimeSpan.FromTicks(dateIn.Ticks), TimeSpan.FromTicks(dateOut.Ticks), x1HourMoney, x15MinMoneyAfter1Hour)
 
    End Function
 
End Class

Public NotInheritable Class Form1 : Inherits Form
 
    Private Sub Form1_Shown(ByVal sender As Object, ByVal e As EventArgs) _
    Handles MyBase.Shown
 
        Dim datePairs As New List(Of KeyValuePair(Of Date, Date)) From
            {
                New KeyValuePair(Of Date, Date)(Date.Parse("12:00"), Date.Parse("12:01")),
                New KeyValuePair(Of Date, Date)(Date.Parse("12:00"), Date.Parse("12:15")),
                New KeyValuePair(Of Date, Date)(Date.Parse("12:00"), Date.Parse("13:00")),
                New KeyValuePair(Of Date, Date)(Date.Parse("12:00"), Date.Parse("13:01")),
                New KeyValuePair(Of Date, Date)(Date.Parse("12:00"), Date.Parse("13:15")),
                New KeyValuePair(Of Date, Date)(Date.Parse("12:00"), Date.Parse("13:30")),
                New KeyValuePair(Of Date, Date)(Date.Parse("12:00"), Date.Parse("13:31")),
                New KeyValuePair(Of Date, Date)(Date.Parse("12:00"), Date.Parse("14:00"))
            }
 
        For Each datePair As KeyValuePair(Of Date, Date) In datePairs
 
            Dim sb As New StringBuilder
            With sb
                .AppendLine(String.Format("Time In  : {0}", datePair.Key.ToString("hh\:mm")))
                .AppendLine(String.Format("Time Out : {0}", datePair.Value.ToString("hh\:mm")))
                .AppendLine(String.Format("Time Diff: {0}", (datePair.Value - datePair.Key).ToString("%h\h\:%m\m")))
                .AppendLine(String.Format(CultureInfo.GetCultureInfo("en-US").NumberFormat,
                                          "Payment  : ${0:n0}", DateUtils.CalculateMoney(datePair.Key, datePair.Value)))
            End With
 
            Console.WriteLine(sb.ToString)
 
        Next
 
    End Sub
 
End Class

    Private Sub Form1_Shown(ByVal sender As Object, ByVal e As EventArgs) _
    Handles MyBase.Shown
 
        Dim timePairs As New List(Of KeyValuePair(Of TimeSpan, TimeSpan)) From
            {
                New KeyValuePair(Of TimeSpan, TimeSpan)(TimeSpan.FromHours(12.0), TimeSpan.FromHours(12.02)),
                New KeyValuePair(Of TimeSpan, TimeSpan)(TimeSpan.FromHours(12.0), TimeSpan.FromHours(12.25)),
                New KeyValuePair(Of TimeSpan, TimeSpan)(TimeSpan.FromHours(12.0), TimeSpan.FromHours(13.0)),
                New KeyValuePair(Of TimeSpan, TimeSpan)(TimeSpan.FromHours(12.0), TimeSpan.FromHours(13.02)),
                New KeyValuePair(Of TimeSpan, TimeSpan)(TimeSpan.FromHours(12.0), TimeSpan.FromHours(13.25)),
                New KeyValuePair(Of TimeSpan, TimeSpan)(TimeSpan.FromHours(12.0), TimeSpan.FromHours(13.5)),
                New KeyValuePair(Of TimeSpan, TimeSpan)(TimeSpan.FromHours(12.0), TimeSpan.FromHours(13.52)),
                New KeyValuePair(Of TimeSpan, TimeSpan)(TimeSpan.FromHours(12.0), TimeSpan.FromHours(14.0))
            }
 
        For Each timePair As KeyValuePair(Of TimeSpan, TimeSpan) In timePairs
 
            Dim sb As New StringBuilder
            With sb
                .AppendLine(String.Format("Time In  : {0}", timePair.Key.ToString("hh\:mm")))
                .AppendLine(String.Format("Time Out : {0}", timePair.Value.ToString("hh\:mm")))
                .AppendLine(String.Format("Time Diff: {0}", (timePair.Value - timePair.Key).ToString("%h\h\:%m\m")))
                .AppendLine(String.Format(CultureInfo.GetCultureInfo("en-US").NumberFormat,
                                          "Payment  : ${0:n0}", DateUtils.CalculateMoney(timePair.Key, timePair.Value)))
            End With
 
            Console.WriteLine(sb.ToString)
 
        Next
 
    End Sub
 
End Class

Public Class Form1
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim fechaini As DateTime
        Dim fechafin As DateTime
 
 
        DateTime.TryParse(TextBox1.Text, fechaini) ' 12:00
        DateTime.TryParse(TextBox2.Text, fechafin) '13:00
 
 
        Dim dif As TimeSpan = fechafin - fechaini
 
        Dim Precio As Integer = 0
        Dim TotalMinutos As Integer = (dif.Hours * 60 + dif.Minutes)
        If TotalMinutos < 60 Or TotalMinutos = 60 Then Precio = 500
        If TotalMinutos > 60 Then Precio = 500 + (CInt((TotalMinutos - 60) / 15)) * 150
 
        MsgBox(Precio)
    End Sub
End Class

 
...
 Dim Precio As Integer = 0
        Dim TotalMinutos As Integer = (dif.Hours * 60 + dif.Minutes)
        If TotalMinutos < 60 Or TotalMinutos = 60 Then Precio = 500
        If TotalMinutos > 60 Then Precio = 500 + (CInt((TotalMinutos - 60) / 15)) * 150
...
 

por ejemplo un auto llego 12:00 y salio 13:00 = 01:00  estuvo una hora el cobro seria $500 

¿si el vehículo estuvo ejemplo llego  12:00 y salio 12:15 = estuvo 15 minutos pero igual se le cobra los $500?

entoces cada 15 minutos depues de la hora deberia cobrarse $150