Before your get too far down the path, please, first define "Professional Video Camera".
In my opinion, that is a video camera with:
Lens filter diameter 70mm or larger.
XLR audio-in connectors.
Low compression video capture (and storage)
When these items are part of the camcorder, then all the other commonly used features/capabilities are "included": Separate manual zoom and focus rings, manual audio gain control, LANC port, proper headphone jack to monitor the audio being recorded, neutral density filter selection and many other controls that are easy to get to and use because they are on the outside of the camcorder - and not accessed through a menu.
The HXRMC50U is part of the "professional" line-up at Sony. Lets check what we can learn about it compared to the above definition:
By appearance and footprint/size, it looks like it is the "replacement" for the miniDV tape based HVR-A1.
It has a single thumbwheel - for manual control focus or exposure or automatic exposure setting shift or white balance shift or iris or shutter speed. You select what you want to be assigned in the touch screen menu, then turn the wheel to make the selection. With the HVR-A1, the single lens barrel-ring is shared manual zoom or focus (selected with a switch on the left side of the lens barrel); exposure, white balance, iris and shutter are all touch screen menu-accessed.
It has a 37mm filter diameter lens. Same as the HVR-A1.
It has an internal hard disc drive and records AVCHD-compressed video. The best the HXRMC50 can do is 24 mbps digital video stream. Higher is better - the A1U does 25 mbps DV/HDV.
It has a single 1/8" (3.5mm) stereo audio-in jack. The A1U comes with an XLR adapter. I suppose you could get an external XLR adapter (BeachTek or juicedLink, among a few others) for the HXRMC50, but that adds another chunk of $ to the cost of the camcorder. XLR connectors are important for using pro-grade XLR based mics.
It does not have a LANC port. The A1U does.
I cannot recommend a hard disc drive camcorder unless there is a specific requirement for really long recording time. The known issues with vibration and high altitude not allowing the hard drive to record reduce the opportunities for capturing video. Flash memory and hard disc drive camcordes record the same file types, so just drop the HDD and keep flash memory or miniDV tape on your short list.
As you have probably already found, the HVR A1U is outside your budget, too, but lets keep in mind that your requirement is to get to $1,000. There is no "equal or greater camera for less". As new product, it is likely finding it for less than MSRP will be a challenge - at least, from reputable dealers like bhphotovideo, adorama, abesofmaine, etc...
The closest I can get you are higher-end consumer cams: Sony HDR-HC9 or HDR-CX550 and if you are not "married" to Sony, add the Canon HV40, HF S200 or HF S20.
One other thing you should consider (if you have not already thought this through) is the editing and archiving environment. We don't know what computer or video editing software you are planning to use. AVCHD MTS files use a lot more computer resources than DV/HDV. So faster CPU and more RAM is a really good idea. As for storage and archive of video from AVCHD cams, the preferred method is to use a RAID1 hard drive array. If one of the mirrored hard drives dies, the other has the video data file - replace the dead drive and the RAID1 capability copies the files form the working drive to the replacement. Chance of both drives failing simultaneously is low (but theoretically possible). With miniDV tape, the tape is the archive, so there's no extra step to make an archive copy of data files RAIDED or otherwise. And since you are looking for least expensive, miniDV tape continues to be the least expensive $/gig storage available.