Here's an article from the Athletic discussing their posted finances from last year.
Wrexham reported a revenue of £6 million... But overall losses of £2.9 million (which apparently is not that dissimilar from other National League clubs)
R&R also invested £1.2 million in exchange for shares and loaned £3.67 million to the club to buy the stadium (which will be paid back to them with interest).
All of this was reported through June 30, 2022. So these numbers do not include money from the TV show, this year's attendance numbers (and FA cup attendance), new sponsorships, or merchandise sold (which has certainly gone up since the show).
If they finish the job and get promoted, they will get an automatic £1 million next season (goes to each EFL team). They will also receive money for each game broadcasted on Sky Sports, which I presume will be quite often given the overseas popularity of the Red Dragons.
Even if they don't get promoted, they're in a good spot considering the loss of £2.9 million was prior to the global explosion of Welcome to Wrexham. They'll be in an even better spot if they do earn promotion.