Yes. But I was wondering if capital costs for baseload gas might be significantly higher, thus making it a less attractive proposition for quick-buck investors.

That not being the case, there are the other arguments you cite, concerning fuel supply. Baseload needs reliable, stable, long-term supply, which may not be easy to get in the volumes needed. Peaker picks up the going market price (unless too high for a profit margin to be made), which makes it expensive.