Those prices don't include the USPTO filing fee, which is $325 or $275 depending on whether it's filed by mail or online.
If you can file the application yourself, you can save on the extra fees by registering directly with the USPTO.
If you need help with the application or find value in the extra services, then it's worth the extra fees. I haven't used LegalSherpa before, but I have heard of them. I have used LegalZoom a few times in the past and have had good experiences. Both are probably good options if you require a legal service to help with your trademark.
Or you can contact a local attorney who can give you some face-to-face advice.
For what it's worth, there is already a registered trademark for "DIZZY" for use on footwear (which is the same class of goods you would need to register for clothing).