VM would really like everybody to pay more, because they make little profit, and by my estimation the broadband business is loss making. Unfortunately, whilst customers may disagree, the UK telecoms market is very competitive, and VM have a continual battle trying to acquire new customers (at a loss making price), then trying to retain them whilst hoping they move onto the undiscounted rates or at least a discount that's more profitable than the introductory offers. That's why you don't (readily) get a renewal offer at the same price as a new customer. There's a load of maths behind why it makes economic sense to discount new customer rates so heavily, covering expected customer sign ups, customer "lifetime", margins, attrition rates, renewal price rates, but those calculations will be top secret from VM's point of view.
Now, from company investor information it is a stated fact that VM have struggled to get ANY increase in the important Average Revenue Per User figure for about five years or so now, despite annual price hikes. So ARPU has sat stubbornly around fifty quid per user per month, and in real (inflation adjusted terms) ARPU has actually declined. The declared ARPU figure is from the mix of hugely discounted new customer rates, "social tariffs", renegotiated rates that are generally a fair bit higher, and a minority on undiscounted tariffs. It's also across the mix of packages, from basic broadband-only right through to the MaxMongoCouchPotato package of highest speeds, more channels of tripe than you can count, extra TV boxes, pay-per-view, and the full set of phone add-ons and any other chargeable trimmings.
Fortunately for VM, along came inflation and higher interest rates, that's enabled Openreach to raise wholesale prices, the customer facing large ISPs all hiked their rates and wrote in inflation busting price rises to their T&Cs, so VM have leapt on this opportunity to hike their own rates. Obviously if enough people leave, or are hard nosed negotiators then the tactic fails. Worst outcome is if too many people take up alternative suppliers, then VM's customer numbers start to fall, in which case VM's essentially fixed business costs need to be spread across fewer customers.
Does this help you any? Probably not, but at least you'll understand VM's business practices better.