IMO, there is a good level of interest in high end Atala, at least among knowledgeable cyclists. However, the marque does has several strikes against it when considering mass appeal for the typical, less sophisticated cyclist or collector.
1. Atala was a full range, Italian manufacturer and did not not have really good sales in the entry level market during the early 1970s bicycle boom. Consequently, it lacks the large consumer base of Atala owners who lusted after the top end racing machine. This is one of the reasons there is such a large market for the Peugeot PX10, despite it being a mediocre, top of the line model. Peugeot sold vast quantities of the UO8 models and these owners now have the money to seek out the PX10.
2. The pro teams that Atala sponsored weren't truly successful. There was no really big name racer or string of victories in prestigious races to afford an owner bragging rights. Most high bicycle owners are wannabes who live vicariously through the racing success of their brand. Atala didn't have a Fausto Coppi or Ottavio Bottecchia with multliple Tour and/or Giro victories to make them popular like Bianchi or Bottecchia. Also, not too many Atala owners want to seen riding around in team jersies (at least on this side of the Atlantic), as the combination of grey and blue horizontal strikes look like they have just broken out of prison.
3. Atala, being a full range, mass manufactured brand, doesn't have the exclusivity of the niche manufacturers like a Colnago or Masi. These are the bicycles that really appeal to the new collector. They are widely known because legendary cyclists like Eddy Merckx rodes these bicycles, even though they were branded something else. The combination of a successful racing heritage and relative exclusivity makes them very appealing to the typical collector.
4. Atala does not have a very good reputation for workmanship. Most collectors who do not have first hand knowledge of the marque, use the internet as a source. The most accessible quide is on Sheldon Brown's site and Atala does not exactly get glowing reviews. Certainly, their were issues, particularly with the low end models during the boom, but most other mass manufactured Italian brands had similar problems. However. many of these other brands had a rich racing heritage to attract the consumer. While the Sheldon Brown guide acknowledges the issues with low end, boom era, Italian bicycles, Atala is, unfortunately, alphabetically first. Consequently, Atala will get a description like "Quality generally ranges from reasonable to downright scary", while Bottecchia will simply get "Pretty much the same quality level and pricing issues as Atala". While the authors are trying to be fair, the average reader would probably not read them back to back and put them into proper context. They would likely consider the Bottecchia to be an average Italian bicycle, while the Atala is to be avoided at all costs. Atala, unjustifiably, has a lower reputation than other mass manufactured, Italian brands and this taints the higher end models.
Due to these reasons, Atala is not in the top tier of collectible brands. Still, knowledgeable collectors will seek them out. They recognize the brand, know the level of workmanship and realize that they can obtain a good deal on the high end models due to general perception. They are one of the better values, in 2nd hand, high end bicycles.
On a side note, your TSX bicycle is not from 1985/6, as Columbus did not even introduce TSX tubing until the 1989 model year.