I have never purchased Avios and have never seen the need. I earn Avios mainly through flying, with a little bit of Amex spend on top. Redemptions tend to be UuA for long-haul flights, and what would otherwise be very expensive flights with AA, AS or BA. We've done some redemptions on CX where this also represents good value for money. We're also doing a one-way IAH - LHR - NCL flight later this year in order to then use a GUF2 on a return flight starting in the UK where prices (especially the carrier fees and taxes) were considerably lower than starting in the US.

If I don't have sufficient Avios in my account to upgrade then I either book a cash fare or else I don't fly at all. If I was going to spend £3,215 then it certainly wouldn't be on Avios.