I've only just become aware of this company, but their website offers an easy way to compare the prices of the various GPs

They are an official ticket agency, not one of these rip-off agencies that don't actually have any tickets!

The prices are not significantly higher than the venues' own prices (comparing, for example, the prices on the Spa GP website)

https://www.grandprix-tickets.com/

France looks like amazingly good value and Hungary are offering a special offer in the Red Bull and Silver 2 stands.