There is being prudent and making no effort horrible as it sounds the league is an entertainment product and teams like them are not going to add to it if they don’t spend at least Forest went up and tried ( although in a slightly mad way)
Using the money to build a new stadium and increase revenue streams to secure a solid debt free future is quite probably the best use of PL money any club has ever done.
There's no guarantee that they won't survive either, especially with Everton quite likely to get a points deduction for numerous breaches of ffp rules, and other clubs possibly following suit.
There are other teams that will probably struggle to finish above Luton, such as Sheff Utd, Wolves, Fulham, Crystal Palace, to name just 4. So everything is possible for Luton, and we may be surprised by their recruitment.