The IAS was founded in the middle of 80's for the purpose to salvage the $cientology the was at that time under major attacks. (court case)
So , they would call it cruisades and IAS becames soon an obligation for any $cientologis to be at least annual member to be allow to buy services from the CO$. One usually gets 6 months free to ''try te benefit of the cult cheap services'' then he has to pay membership.
At the beginning it was independent (apparently) from the Church but it is not anymore.
One can easily give 100,000$ and more , to 1,000,000$ in his life
Selle the house and everything to ''ensure'' we can ''save the planet''
When it's time for higher OT level - you better have contribute a lot or there will be a little problem here