The rate that Unity was seeking, is I believe in line with what is charged by Epic for the UnReal engine but with a much reduced threshold.
Absolutely it is not "in line" with Epic, because it was a flat fee, not a percentage.
Unreal charges 5% of revenue once you earn over $1m.
So you actually have to be bringing in money to get charged by Unreal. With Unity, because it was/is a flat fee per install, you could very easily be charged vastly more than you were making, or a vastly higher percentage (even ignoring the lower threshold).
If you were making a very large amount of money, Unreal would actually take more. But they less financially successful you were, the cheaper your game was, the worse Unity's fixed fees were going to hit you. This is obviously perverse as hell, because Unity is primarily used for lower-end, lower-price (or even free) games, whereas Unreal is primarily used for higher-end products. Unreal also are willing to negotiate - a lot of devs that use them are paying much lower rates than 5% - including down to zero in some situations (as Epic themselves say on their website) - I suspect given the wild uptake of UE5 that they have been negotiating pretty generously of late (I very much doubt WotC would be willing to give away 5% of revenue on the 3D VTT, for example, but they're using UE5).
At 20c per install, if a product was only ever installed once, Unity would have been cheaper for any game which cost $4.00 or more. But that's if a product was only installed once. Ever. Which is very unlikely. As they were proposing to charge per install, we should multiply that by at least 3, and suddenly we're looking at a situation where an awful lot of Unity games would have been cheaper with UE - and UE's fee was keeping a lot of devs away from it.
