You have to buy tickets to Challengers in Belgium? In Australia they are free. Even Grand Slam qualifying is free.
And that is the difference about how tennis is viewed and promoted in Australia compared to the Americas and Europe, even India.
There the Challengers draw a sizable crowd, especially to the semis and finals, normally held on a Friday and Saturday evening and on the weekend, whilst in Australia you get a few officials (have to be there), the player's family member's (if playing near home on the weekend or night), perhaps a few club members (if at a club and they came to have a hit and the courts are full (damn) so just watch a while), the lansdscape gardener and a few passers-by.
In the USA, parts of South America and various places in Europe, entrance fees for spectators to the semis and finals are normal place. Australia is a real "back-water" when it comes to promoting tennis and the level of interest in the general public. Not even so-called "tennis nuts" from the tennis clubs will take time to go and watch a Futures or Challenger event, even if there are five or six top ranked Australians playing.
Having said that, even the player facilities and amenities are far superior to that in Australia, and the player's are all treated as celebrities, which does not happen in Australia, especially Sydney. Playe's parties are organised, promotional functions, dinners, etc. In the USA, at most Challengers (and some Futures) tournaments, player's get billetted, which helps heaps with costs. Not in Australia. At a Challenger this year, an overseas player from Canada, playing in the Main Draw, was told he could not get the official transport as he was not staying at the official hotel in Homebush, but he was staying not far away, just outside Homebush in Newington, where he was sharing to save cost. Oops, gone off on a tangent there...
Perhaps more should be done to promote (advertise) the tennis events in Australia, especially locally.