I have also used gCloth, and I think that will save you money. I think the disposable inserts are great for traveling and such, but really are more appealing for their eco-friendly nature (since they are completely biodegradable) rather than cost savings.
Re: If you use g-diapers
We use them with gcloth, so yep they save us money. The disposable inserts are more expensive than disposables (especially generic).
I have 16 medium covers an 24 gcloth inserts, but that's for two kids - they are in the same size.