Professional? Hahahahha don't make me laugh. This isn't anywhere near professional.
You talk about "360p" and "1080p", but that's about video, not audio.
And your prices are way too low to sound professional. Any mixing and mastering I have done is generally around 70$-100$.. And THAT's good. We talk about 24bit lossless wave files. Not about video... Also, if you send a low quality preview, it kinda defeats the purpose of judging whether it's a good mix or not. Due to compression.
Aside from all that, this is just pointless spam. Most of us thrive to learn how to mix our own tracks, and THEN send them off to mastering.