Lets put a notional figure of €5000 on those costs.
Firstly- it is always a risk that costs cannot be recovered.
It is likely that the costs will have to be taxed - i.e . approved by the relevant Court authority.
That approval then becomes an Order of Court and becomes a Judgment against the losing Plaintiff.
The Judgment is then tried to be enforced by all the usual means e.g. Sherriff, registration ( which affects credit rating), judgment mortgage if there is a property to be attached and, if all else fails, an instalment order followed by committal, if failure to pay is wilful.
Your somebody needs to talk to a solicitor about the process.
Bankruptcy would be a bit extreme but, yes, presumably, that would render the losing party unable to pay.
mf