Lapland

For flights from Helsinki to Lapland (e.g. Rovaniemi) use FinnAir's "Flexible +/- days" fare calendar search. Depending on day of the week fare difference can be substantial. https://www.finnair.com/us/gb/

BTW Rovaniemi is just south of the arctic circle and mid December is close to winter equinox - 2 plus hours of daylight and the daylight could be cloud obscured. https://www.timeanddate.com/sun/finland/rovaniemi?month=12&year=2017

If you want to meet Father Christmas, the Rovaniemi tourist attraction is Santa Claus Village: http://www.visitrovaniemi.fi/attraction/santa-claus-village/

We visited Lapland a number of years ago much further north flying in to Ivalo, northern most airport served by FinnAir. Great experience skiing amongst the reindeer but not for most tourist. Sami hunting village can be pretty rudimentary in amenities. The holiday lodges mostly cater to Finns and tourist looking for something exotic such as ice hotels.
https://www.lonelyplanet.com/finland/lapland/ivalo

A small town by most standards, Ivalo (Sámi: Avvil) is a metropolis in
these latitudes. With plenty of services and an airport busy with
Christmas charters, it’s a useful place, though with few attractions.
However, Inari’s Sámi culture and Saariselkä’s plentiful activities
are close by.

There was bus service from Ivalo Airport to Saariselkä. The Urho Kekkonen National Park is adjacent and considered the true home of Santa Claus: http://www.lifeinlapland.com/articles/lapland-travel-tips/real-home-santa-korvatunturi.html

https://en.wikivoyage.org/wiki/Urho_Kekkonen_National_Park

Urho Kekkonen National Park is located along the Russian border in the
municipalities of Inari, Sodankylä and Savukoski. The park includes
Korvatunturi, where Father Christmas lives – at least according to the
Finns....

The western border of the park is by national road 4, i.e. E75
(Rovaniemi–Sodankylä–Vuotso–Tankavaara–Kakslauttanen
(Kiilopää)–Saariselkä–Ivalo), with several coaches daily, including
coaches from Ivalo to Saariselkä and Kiilopää and coaches from
Nordkapp, Karasjok, Vadsø and Tana bru to Rovaniemi. You could come
e.g. by plane to Ivalo or Rovaniemi or by train to Rovaniemi and
continue by coach

We started and ended our Lapland ski tour at the Kiilopää Fell Center just outside the National Park. The Fell Center is served by coach from the Ivalo Airport.
http://www.inarisaariselka.fi/en/companies/fell-centre-kiilopaa/
.

"I don't want to spend $600 + for a eurail pass and buy a ticket."

If you just need that one ticket, why would you buy a Eurail Pass? Just buy that single ticket, from Finnish Rail. Details on that train from the rail guru, The Man In Seat 61, here: https://www.seat61.com/Finland.htm#Train_travel_within_Finland

To find flight options, use Skyscanner: https://www.skyscanner.com/

If you prefer train over plane, the Finnish Rail website is: https://www.vr.fi/cs/vr/en/frontpage

Discounted tickets for regular adults are available with advanced purchase. Pensioner/senior discounts were better than advanced purchase. Finnish trains are comfortable and have on-board wifi to pass the time while watching the trees go by. Long distance trains have food service cars.

Note that the train journey from Helsinki to Rovaniemi takes more than 8 hours with at least one train connection. Saariselkä is reached by long distance coach from Rovaniemi.

https://www.vr.fi/cs/vr/en/travel-lapland-finland

https://www.vr.fi/cs/vr/en/rovaniemi-en

https://www.vr.fi/cs/vr/en/inarisaariselka_en

thankyou so much for all the replies - some very useful info - ill put my head down and research