Unbranded tablets on amazon seem to sell for £50, you could probably find some from a shop that price (just make sure they run android) and then you can airgap with electrum without buying something more specific/expensive.
I'll be more wary the security patch of these unbranded tablets if up to date.
I'll go buy trezor if the price is just little different.
Buying a $250 HW is insane, if the whole purpose is the same to a fully secured and cheap one.