In the US, the 05 Xstars run from upper 30's USD to mid 50's USD. I do not know if they offered salt water series back then and if so, you need to double check if the one you are looking at is equipped. Personally, I would run for the hills if it has been parked outside in salty air and has been run in salt water. Also, prices can swing widely depending on options (some of these boats have $10k-$15K+ in stereo equipment alone). Here are a couple of examples of 05 Stars in the US:
If for some reason you want to pursue this boat, your next questions should be hours on engine, maintenance records, mechanical shape, visual shape (how are the seats/vinyls?, all gauges work? ballast work?, how is the trailer, etc. etc.). If for some reason the above passes your initial smell test, get it to a mechanic and have them check it out or better yet, get a certified marine survey.
If you search this forum, you will see several detailed check lists on what to look for when purchasing a boat.
3 items in your post are going against you at this point:
1 - Salt water
2 - Stored outside
3 - Price