ok, no one asks you to buy this great software, merely the majority stimulate you to buy because it is great.
If for whatever reason you willh have to buy a new scanner and it is not supported by OS X it will very likely be supported by VueScan. Just because you rarely use it doesn't mean the price is not acceptable, specially seen in the light of the (sometimes too abundant) new versions of VueScan including more and more scanners and increasing the level of quality.
But you have made your point: too expensive, but then you work and get paid a minimal wage no doubt - even a developer needs to buy food to say the least and this price for this great piece of software is not overasked: you may install it even on several CPU's in one home.