low bottom end. £20 (yes a little more than today to temp you towards better models for a few tenners more)
small, flat, small monochrome screen, basic phone facilities, small aluminium ion battery, 1-2 days charge.

med bottom end. £25-£35
4-6 days charge, sms, little monochrome screen, basic phone, google audio search + wap maps, small aluminium ion battery and flatter than today's bottom line phones.

high bottom end phone. £35-£50
3-5 days charge, small phone, small colour screen, video conferencing app ability, google audio search + youtube,mini streamer, wifi and 3G, 4G mobile, flat, aluminium ion battery.

Top of the range nokia mini phone idea. £85-£140
Very resistant to damage and with long life use in mind, small, small colour touch screen and buttons, 64GB emmc, 1-2 weeks charge, video conferencing, google Audio search + youtube, mini streaming , aluminium ion premium battery, chunky, wifi/3G/4G/satellite, Also you can use it as a bluetooth hotspot.

mid range £55 - £140
This is where your budget smart phone goes with all it's features (yes a little less than today giving more people access to a decent smart phone around the world)

high range £140+
all sorts of stuff goes here as we all know.

don't expect full blown smart phones to drop below say £55 in the UK just because they could make them more lite added with the savings of using aluminium ion batteries and just how much more efficient mass manufacturing will be in five years. even if inflation has got down to pre-covid levels companies will make profits if you can afford for them to. Just because some company could produce very high quality caps at a fraction of the price premium cap are sold doesn't mean your company doesn't just fit it's price best to profits.
A budget smart phone today has wafer thin profits all that will really change is that the price goes down a bit for some ranges and more profits are made. why because so many people will likely have £55-£140 pound to spend on a phone if they are on a budget. the Lower phone range would be more for poorer groups in the world with a small selection of such products available in the UK although the nokia idea might be a big seller.