BA Avios reward flights – baffled

[Bearing Up]

I have been reading the various reviews re the above given I’m looking into the 2 of us flying LHR to FRA in Dec.
The HfP chart lovingly pulled together by Rob and published on 2/6/22 indicated the above flight as 4750/5250 one way off/peak times in ET.
I have looked at booking the same flight, out on a peak date in mid Dec, back on off peak late Jan and BA wants 38000 Avios & £2.
Using the HfP chart I get the math to be 10.5k out and 9.5k back making 20k.
Am I making a schoolboy error? Why the difference or can BA just do what they want re Avios pricing given supply/demand?
Thank you in advance for the correct guidance.

[SamG]

His chart assumes you are selecting the £35pp “tax” option – you can use more Avios to pay less cash but this is usually a poor deal in value per point terms

[Bearing Up]

Sorry for the delay in responding @SamG, required elsewhere.
Now I am confused. Selecting the £35 tax option? I merely went into reward flights, detailed what I wanted and the Avios cost was produced.
Is there another site/option offered that I should have used?
Thank you.

[ChrisC]

As part of the booking process just beneath where the cost in cash and avios is displayed’ is a line that says ‘other pricing options’

Click on that and you get a range of varying avios and cash components.

[Rob]

The prices in our chart are the ‘historic’ prices and, more importantly, what you pay when redeeming a 241 voucher.

BA will offer to rip you off by giving you the chance to use more Avios and less cash, but you should resist this.

[Bearing Up]

Thank you ChrisC and Rob for your replies. I am aware of the ‘math’ involved and did see the other Avios payment options. I wasn’t aware the chart was based on use of a 241 voucher but helps clarify matters.
Thanks again.