Well that was a good laugh.
Signs need to be put on something. If there isn’t a suitable ‘something’ there already, that means erecting posts, and that means digging a foundation, and that means doing a buried services check. That makes it, easily, £500 a sign.
If the phones are there for crossing users to seek advice if it is safe to cross, then the phones are safety critical. Regardless of technology, they will need a power supply, and a secure equipment box, positioned in a place of safety. Again, that will likely need to be constructed, involving some digging. That’s thousands.
As it happens, I have in the past installed phones on a number of level crossings, and it was in the region of £25k a crossing. That was more than a decade ago.
Then there’s the signallers workload. I know of at least two signalboxes where the provision of a number of new crossing phones increased the workload to the extent that a second signaller was required simply to do the crossing workload. Fortunately in both cases resolved through technology (at the costs of many millions). It’s reasonable to assume this would happen again somewhere else.
And at the end of the day, you have spent all that money, and you still have a level crossing. Far better to spend a bit more and pay the farmer to close it. Then it’s never a problem again.