Totally, but if the work done @home is useful, donating compute time makes economical sense I think.
If I'm willing to donate $10 I can either donate money and it may be used to buy $10 worth of compute, with should cover all costs including the hardware and administration.
Or I can donate $10 worth of pure electricity and the other marginals I cover for no or a very small extra cost, since I already own the hardware for other purposes which it's temporarily not used for.
In the latter case the value of my $10 is higher, I theorize. Again, given that the @home project is truly useful.