According to a new paper by Aviv Yaish and Professor Aviv Zohar:

1) Mining ASICs are overpriced.

2) A portfolio of Bitcoins can imitate (and sometimes outperform) returns from mining hardware.

3) Bitcoin's volatility should increase rig price.

Medium post: https://medium.com/@aviv.yaish/your-asic-is-probably-mispric...

Link to paper: https://arxiv.org/abs/2002.11064