Put some sort of vendor price check into TSM without visiting vendors
TSM shouldn't tell me salt is a good deal at 2g, when a vendor sells it for 50 c. until I visit a vendor that sells salt.
This a bigger issue with recipes...
This should be enough:
Options->Tooltip Options->[V] Display vendor buy price in tooltip.
If the problem is with gathering module, make sure you have "vendorbuy" included in the matCost:
Options->Module Options->Crafting->Default Material Cost Method = min(yourCustomPrice, vendorbuy)
Then, if you find an item that is only sold on limited supply, but TSM displays and uses the vendor buy price anyway (for example with Bronze Framework), you can do an exception, and set the custom mat price for it:
Options->Crafting->Materials->Bronze Framework->Custom Price per Item = yourCustomPrice
Doc 309 commented
If I understood the helpful folks in IRC last night the main hard part is adjusting the price for reputations etc...
A simple tooltip line saying "This item is sold by Vendors." would be good enough for me.