This is not a for sale thread, but I want to sell off the aluminum lower off my 553 pistol to get a Steel one.  It is New Take off, no stock plate, no push pins.  Having a hard time finding any pricing since they are different than all the 556 lowers on the market.  

Edit. Sold by mid day on Sturm. I feel it was a fair price. More than $100 less than a steel but more than a US one.

This probably won't help but I would expect it to sell for way more than a run of the mill 556 lower but less than a 55X steel lower. Mostly because I would think it would fall into the category of collector's item... the people just looking for a SAN mag lower are going to buy the US made 551A1 lower and most of the hardcore SAN perfectionists are going to lean towards the steel Swiss lower.

The complete SAN rifles with aluminum receivers sell for slightly less than the steel lower models. A SAN 553-1 diopter model with steel lower has a MSRP of 3930 Swiss Francs while one with the same features but the new aluminum lower has a MSRP of 3850, a difference of 80 Swiss Francs or 91 US dollars. I figure go with the lowest price you see for a black steel 55X lower and cut 100 bucks off that price... that would be my starting point for selling it.

The problem is you need to find a buyer, and most likely due to the price point of the lower and the very tiny market of folks looking it will probably either sit for sale for a while or you will have to whittle your price down until someone bites. OR you could win the sale lottery out of the gate and have a buyer in an hour. You never know with these things... its like trying to sell a Ferrari... the item has value and everyone agrees it has value but hooking a buyer is the hurdle.

I agree with most of the above, but I'd be surprised if you got that close $ wise to a steel lower. I suspect, it would be much less.

You also need to consider the market now has the 551A1 lowers out and about.  Sig NH, was selling them with a stock for less than $400 a few years back.  I purchased a SANS lower for my 552 replica and was offered $250 for the 551A1lower.

I have sold three Sig USA lowers on Gunbroker and have gotten $355.00 for an AR mag lower with the sliding and folding stock.  $300.00 for a Swiss mag lower without the stock, and $325.00 for the early AR mag with the AR type sliding stock.  As far as your 553 lower, you did state that this is not a "for sale" post, but I would be interested in it if you want to IM me.