Well, I'm going to defend Dave. He's a great guy and I do a good bit of business with him, and he's unwaveringly honest and straightforward.
Yes, steel prices have gone up dramatically, and I'm sure this has something to do with it. There's a lot more to the story though. Everybody always seems to think "hey, that's 50 bucks worth of steel -- what a ripoff!" This is an ignorant statement to make. Shops like Dave's have overhead (lease, utilities, equipment, insurance, employees, etc.) and need to make a certain amount of profit on goods sold to cover this overhead. To do this, they price their goods and services at a point that they feel the market will bear. Due to the law of supply and demand, margins will be higher on some products than others. I know for a fact that Dave isn't getting rich off of IRS install kits, and if some publicity and a surge in demand allow him to charge a bit more, then more power to him.
How many hours do you think Dave spent developing his kit? I have installed several and his kits and instructions are perfect. How much liability insurance do you think he must carry to sell such a safety-critical item? How much time do you think he spends on the phone and in front of the computer answering all of your questions before and after the sale? All of these things cost money, either directly or indirectly.
As stated above, there are alternatives for performance suspension out there for less money. The fact is, if you want independent rear suspension and don't want to do it all yourself, the DVS setup is still by far the cheapest way to go. CTM Engineering T-5 IRS (the vintage Ford one) averages $7500 in parts. The Heidt's IRS averages around $5000 and takes a lot of fab to install. The new Blue Moon/Control Freak IRS is over 9 grand with no 3rd member. With DVS you can manage a great IRS for well under 3 grand if you try.