Salvaging exotic insignias and inscriptions that are not craftable is a very profitable business and in my opinion, the best specific advice yet on this topic to make 10 gold (on average) with just 10 minutes of your time.
Why is that so? Because the salvage rate of isnignias/inscriptions is not documented as good on the wiki as for example ecto salvage rates and upgrade salvage rates (which are determined by the salvage kit you use and is fixed). Its also way harder to filter the tp towards a group of gear that offers insignias/inscriptions for salvage due to named armor sets and weapons.
I know that mystic and me have a far higher sample size of salvaging those than the wiki offers, through pms. Personally, i salvaged over 2k exotic sentinel gear (which droprates got reintroduced into the economy after Flame&Frost with the Ultimate Citizens Rescue Bag /UCRB) for defeating Scarlet). This profit scheme is over but i would just like to explain how i profited so much from it.
If you search the tp for sentinel items and put the filter to exotic, you will get 99 items.18 are crafted for each armor profession, plus 19 for each crafted weapon and plus 3 for sentinels bane and the inscription and insignia. So overall, 49 exotic weapons and armor with sentinel stats got reintroduced through a possible drop from the UCRB. You might have never got a drop of those but in general, the market got flooded with those without being noticed. As their supply was pretty scarce before the last LS updates, nobody knew that you could actually salvage Sentinel Inscriptions and Insignias. I knew because i checked. And in those 4 weeks I salvaged about 2k exotic Sentinel gear, which i got between 1-2g (due to the increased drop rate) and sold them between 7-10g. At the start, i used up all my BL savage kits on this but later found out that master salvage kits would yield the same profit, if not more.
You wonder why i make so much profit? Its because i take a chance and know a market before anybody else. I told this tip to some people in my guild, they bought some sentinel gear directly and salvaged 5 of them for 1 insignia, not making much of a profit.At that time, I salvaged more than 1000 and they wouldnt believe me that i would make a couple of guild wars 2 gold profit per salvage.
If you want to make good profit on the tp, dont look for flipping or speculating, look for items that drop much due to the current game meta and look what profit you can make out of it.