I will try to help ...
At minimum, an RTA Cup Series charter is, at least, worth the weekly payout percentage difference between chartered and non-chartered entrants X 36 races X 3 years (the minimum allowable period of ownership based solely on performance).
In 2015, the last year for which payouts were available for public consumption, the 20th place car in the standings was the 16, driven by Greg Biffle. Middle of the field. Roush-Fenway Racing earned $5,555,.082 in prize money for that car in that season. The rumor mill suggests that in the present, a chartered car earns 30% more than an unchartered entry. For the purposes of this explanation, let us assume that is true. If you like, you can do the arithmetic with different percentage figures.
So, if the 20th place car earns the same amount this season and is chartered, it will have earned $1,666,746 more than it would have if it it was not chartered. Multiply by three years ... $5,000,238. There are other factors that play in. Additional TV revenue dollars accrue to charters above and beyond the weekly payout. On the downside, if a team leases its charter out for a year, it must use it in the following season or sell it. That could / would have the effect of de-valuing the asset.
I hope this has helped. .