But the winning money from both leagues is about the same,
Still You're wrong. It is impossible to build in one season team, which is able to win B3. So You have to count money earned in many seasons, not only in one season.
All teams playing in first division in my country started in lower divisions (6x III division, 8x IV division, 2x V division). So they had smaller incomes for many seasons, whilst You had always maximum incomes from beginning. One season in lower division means much lower incomes, it's more important than these few cents from TV contract. And therefore You are able to develop Your team faster. Please count 6 seasons and it will be obvious that Your incomes were much higher. It's FACT and it's simple math.
And I'm sure that in future Your TC contract will be higher, even the same as in big countries (when level of competition in Your league will be higher). Meanwhile incomes in 2nd league always will be worse.
minus the extra rounds teams in larger countries play in there Cup, compared to ours.
It's funny. You have no guarantee that You will win more rounds so You can't count these money. And I'm sure that money for winner in 6th round in cup in Your country is higher than money for winner in 6th round in cup in my country. In Your country it's 100k, in my country it's 50k. It's unfair.