That price is nothing short of a theft!
Mine is like this, I would of got similar to one on your link, but my local shop did not have such, only these:
https://www.worldofpower.co.uk/husqvarna-5056981-09-combination-gauge-325-1-5mm-h25.html
I don't like that roller guide, not sure if it is my technique or what, but don't like it.
Do you have local shop that sells Husky stuff? I found these two, not sure about postage trough them though, but I think 2-3 pounds from local shop on such tool, tenner from it is quite steep, imo. even with the postage added.
https://www.worldofpower.co.uk/husqvarna-chainsaw-filing-equipment.html
http://www.buyamower.co.uk/product/husqvarna-depth-gauge.aspx
My old depth gauge is similar to this Stihl version, (Price of 1.75 FIM is written on the tool, that is 0.29€, inflation from 70's to these days
);
https://www.worldofpower.co.uk/stihl-00008934008-325-depth-gauge.html
Problem with this kind of depth gauge is that it averages out cutters, I believe long part should be kept against the cutters, which leaves raker height high, holding it down so that tool will be on angle, might not be so easy to do consistently enough as 0.1mm is a lot of difference there I believe.
Husky tool clicks on place, slot at the edge of tool goes over chain, near rivet, while shaped slot goes over raker, it also results top of raker being filed to angle, that other type of tool, or then me too have not understood how to use that Stihl kind of dept tool properly, but that is how videos show it being used, so I guess I'm using it right.
Now with Husky tool I indeed filed the top of raker with the tool, then rounded it gently to fin profile, it takes only two or three light passes to get it reasonably fin like.
If your chain gets dull really fast, then it could be that you file it too deeply, or just the sand and dirt on wood you did cut. I doubt that with file guide one could do hawk's peak kind of cutter shape, which can happen if filing without the guide, but it is something to be aware of.
When you put pressure towards ground when filing, file eats itself into chain links and starts to make really sharp feeling beak of the hawk shape cutter, which will dull fast as cutters edge will fail when it touches wood, so when filing without guide one needs to kind of lift the file but at the same time push it gently towards the cutter, or that is what I have undestood.
So if chain runs 3 to 9 when horizontal, force you push file against the cutter might be something in 1 to 2 direction. That is very hard to do when trying to keep file on that 30 degree angle and handle 10 degrees down, while file is biting into cutter so that it stops moving!
With Oregon's filing guide I don't need to think about that aspect, I just keep file horizontal and 30 degrees angle with very mild pressure towards the power unit.
I'm not sure about this, but if chain feels really really sharp on thumb, like a really sharp knife, it might be that it has hawk's beak shape on cutters, I know when I use my cheap grinder, I don't get that sharp feeling chain, but it might be better now that I think about it.
I know that when sharpening axe, it is possible to get really sharp feeling edge, but it will not hold edge as there is so little material supporting the edge.
There is lot to learn for me too, but I guess slowly some understanding of how chain actually works is getting into my teflon coated thick head, until some pro tells that I have got it all wrong once again
