It's underpriced then, unless you expect a very big jump in difficulty, when you take into account the interest from lending it.
I expect 5%-20% jumps in difficulty every 2 weeks.
It will depend mainly on the bitcoin price in USD. As long as it doesn't increase significantly, I'd expect small difficulty jumps, like the last months.
I have bought some TH1 to lend them, so I can find out how it works in practice.