it is hard to quantify 'expensive' - when your business relies on it. If not having your computer and data put's you out of business you may have to have it repaired - but if buying a similar machine and putting your data on it gets you over the line, that's fine too.
Maybe you should let a good professional handle this - I have seen to often that business owner panic at a computer breakdown, because they see their business being threatened - and it is hard to stay calm and objective when troubleshooting if your financial existence is at stake