Why are equipment racks so expensive?

You certainly must do your research, but high quality audio racks can be considered a component. Not if you have $500 components, but if you have $10K or higher.... and particularly on turntables and tube equipment. They must be rock solid... many contain vibration isolation mechanisms or may be designed to do that. Like any other component you have to match appropriate spending the overall quality of your system.

I agree with ghdprentice’s remarks about choosing a rack that is in a price tier that makes sense in relation to the cost of your components. Like you, I have used Ikea products: Ingolf stools as speaker stands for about five years. I chose to buy Skylan stands as an overdue upgrade for my Harbeth speakers. (Yes, I’m aware that some here are certain that I should have bought stands with open bottoms, but that ship has sailed.)
I recently chose to upgrade my rack from a basic Sanus model with glass shelves that served me well for about ten years. Its replacement is a Symposium Foundation Ultra rack, which cost almost ten times what I paid for the Sanus rack. The differences between the two racks are substantial too, from design to parts; and the Symposium is U.S. made. I would have preferred that the new rack had cost less but chose to buy it anyway. I believe that my system sounds better partly due to the new rack and recently purchased speaker stands. I funded purchase of the new rack with proceeds of sales of some used equipment.
There are basic racks available for $200 to $300, followed by more attractive designs that are somewhat sturdier in the $500 to $1,000 range, and then more expensive options, up to $10,000 if you have funds to afford that. 

Buy what you like and can afford.  No big deal. Just like cars, watches, fine cutlery etc. You can find the tool to fix your issue. The price points vary but seldom do the more expensive ones outclass their lower price counterparts by the margin of the price differential. Does a Rolex tell time 1000% better than a Timex?  

"You certainly must do your research, but high quality audio racks can be considered a component. Not if you have $500 components, but if you have $10K or higher.... and particularly on turntables and tube equipment."

Ridiculous Dollar cap statement on gear, IMO.

I have a Pilot 232 EL84 tube amp that I prefer to any ARC tube power amp that I’ve ever listened to (think I paid $200 for it) and other than reforming the lytics and replacing the ceramic cap that feeds the 5ar4 rectifier it’s stock.

My Thorens TD125 MKII/SME combo was $225/shipped and I decided to keep it after placing it on a properly implemeted Greater Ranges shelf.

My CAL Icon MkII was perhaps $400 and after placing it on a Greater Ranges shelf I sold the Bel Canto DAC I was using @ the time as the stock deck sounded better to me (on the shelf).

This said, my electronic gear is located outside the listening room (see system details) and yes a decent rack/shelves has still greatly improved the SQ of my source components.

As far as my tube power amps and preamps I simply use the stock shelves (having tried the Greater Ranges) as there was little difference in SQ (again taking into consideration that the gear is NOT located in the listening room and that even the stock shelves are supported by upturned adjustable brass spikes).

DeKay