I’ve found spares when looking on eBay etc pretty reasonable. Whole engine for £300 etc there seems to be a lot getting scrapped so second hand parts are freely available. Also bits fit across 924/944/968 too which helps. I’m sure something will cost a fair bit but all cars can cost a lot at some point .
Values should rise too over next few years. I think we are looking at a fair few years until Boxter values rise. Plus I needed a 4 sweater for me and the kids.