Schematics can be purchased with the TSC Currency in the game, and while developing the system, all the prices were artificially hiked to prevent purchase of them.
These prices have now all been set to the correct values as we see them, and are now available to buy with both credits and TSC, so you have the choice.
All Schematics have a build limit, whether purchased with credits or TSC. Once you have used the schematic up to the build limit (displayed on the schematic view in the stores, and also in the crafting view) the schematic will expire (auto destruct) so crafters be sure to take this into account when pricing your items!
The primary advantage of purchasing the schematics with TSC over credits is that you will get a much higher build limit than with the credit purchased schematics.