Last week, Cramer identified Voxejet as one of several stocks that were part of "bubbling" across niche sectors, including organic food, cloud computing and 3-D printing. Cramer reiterated his position Tuesday.
"Three-D printers are insane," Cramer said. "Now I am going to be attacked … on Twitter because I said these stocks were expensive. But I want to say, everyone has a right to overpay. I would never get in the way of people's right to overpay.
"When Voxeljet becomes an earnings story, I am willing to listen. But right now they are the poster boy for overvalue," he added.
In contrast, Cramer cited Workday, a provider of human resources software, as a pricey stock worth buying.
"This is the most expensive stock I follow, and I think it's going to go higher," Cramer said. "Go long Workday and short Oracle, I think that's a great pair trade, as they call them in the game."
Cramer's charitable trust does not own shares in either Voxeljet, Workday or Oracle.