They did that for the second gen meters.

"The first covers newer, second generation (SMETS2) meters, where only the communications module needs swapping out, but even this is likely to cost £1.3 to £1.4 billion (c $1.7 to $1.9 billion) before the hardware cost of each new hub is even factored in.

The other is for an estimated 7 million older, first-generation (SMETS1) meter installations, which have the cellular comms hard-wired in, so the whole meter typically needs replacing. The report authors estimate this will cost another £2.1 billion to £2.45 billion ($2.8 billion to $3.3 billion), at an indicative replacement cost of £300 to £350 per installation."