Sturdy Turntable Stand

Yep
Build your own as I did as I was saddened by the prices being asked.
4 lengths of all thread rod, a number of nuts and washers and 4 pieces of 2 inch thick maple 24x18.
One drill, couple wrenches, couple hours and all done.
Infinitely variable shelf height, level any shelf in seconds.
Cost?
$300 max.

Right. That is pretty much what I did. DIY.
Next step up from what uberwaltz built, incorporate a sand bed into the shelf the turntable will sit on. Next step up from that would be what I did, cast the shelves from concrete with a sand bed cast into them. With a granite machinists plate on top its massive and stable and near impervious to footfalls and other vibrations. http://www.theanalogdept.com/images/spp6_pics/C_miller_web/TTstand_1.jpg Mine isn’t adjustable but it is modular. The legs are ABS filled with concrete and bolted together with the shelves so it can be moved one piece at a time. Altogether its near 700 lbs and, you might say, rock solid.
This is kind of old but you get the idea http://www.theanalogdept.com/c_miller.htm

@uberwaltz
I've just started looking for an audio rack for my son, I'm giving him my RP 3 and some other pieces. I like your DIY rack and wondering what did you use for feet? 
Eric