Well as always it’s never about saving money, it is very very rarely cheaper to just buy a new bike, repair is normally always cheaper unless you’ve knackered everything! so you could repair it cheaply*, but if you want a new bike go for it 🙂
* how cheap is up to you, if it is just the drivetrain that’s knackered, well cassettes are £10-20, chain is £12, even rings/chainset could be done for <£50. Even a complete Tiagra groupset @£200 + some wheels for <£100 would basically turn it back into ‘new’ as the frame won’t have worn out. If it’s just a workhorse then 2nd hand bits or trickledown from upgrades (yours or friends) can make it even more cost effective. Do you have a local bike project/recycle scheme?
Frame also has a groove under the bb where the cables worn through
For this frame and for future ref, get some of the clear/black cable liner from sealed cables, run a short length under the BB and run the cable through it, should help massively with the above problem and changing a bit of cable liner once in a while when it’s worn out is easy.