Amongst the figures that are thrown around whenever these are discussed within the treasury are the cost/loss vs benefits.
I am in no way in favour of it but as an example take the idea of the ending of the highest rate tax band. The actual cost to the treasury was miniscule in terms of the overall tax revenue because the numbers affected were less than 1% of tax payers and it only applies to their earnings over the threshold anyway. If, as the theory was, it encouraged them to return/stay and employ more people bumping up tax revenue way more than the losses then it is an overall benefit to the country. They employ the likes of drivers, secretaries, cook, houskeepers, gardeners etc. all paying tax in this country if domiciled in this country
The subject was far more emotive than the issue it represents which is always a problem when it comes to taxation.