Wow... That was some big bucks in 1990. Yeah, I love mine and I feel your pain.
Well, first off notice that it appears to be a sale made in Canada apparently using Canadian dollars.

In 1990, a Canadian dollar was equal to about 85¢ American. Next, subtract out that hefty 8% sales tax... and you come down to an equivalent pre-tax US price of $709.75. I'm not sure about any import duty or other tax that Canada might have assessed back in 1990.
Coincidentally, that's roughly what an "
unfired-new-in-box-with-all-paperwork" Model 4006 would sell for today in my area.

Plus you could probably get even more money for it on that certain large firearms auction site.
Of course, we can now look at inflation and the shrinking value of both the Canadian dollar and the US dollar.

Using various government indices, that $709.75 becomes somewhere between $1,284.65 and $1,334.33.

Let's call it $1,300.00.
So what does a full-size stainless steel .40 go for in today's market?

One good comparison might be to the Beretta 96FS INOX... street price between $600 and $700. Beretta's newer, fancier models go for more.
On the other hand, the Sig P226 Elite Stainless .40 is nutty expensive at $1,396.00 list. True average street price is hard to find because "Sig" and because there are relatively few out there for sale... but I'm guessing something well over $1,000.00 for sure.
