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10 yo has a starter lego train set and absolutely loves it. His 11th birthday is in a few weeks and he has asked for more tracks and possibly another train. He has always liked trains and lego so this combination is ideal.
Apart from the lego shop and amazon, is there any other places to get hold of tracks etc at a reasonable price?
EBay, loads of lego on EBay. Train tracks can still be quite pricey even second hand.
Lego compatible from China. To hell with paying Lego prices.
https://www.aliexpress.com/popular/lego-train.html
Places like bricklink sell new and second hand stuff. Ive used it a fair bit and have had no problems so far.
Track is expensive. There is a reason there are a load of obvious split sets for sale on eBay. I've ended up with a fair load by being patient and either buying second hand full sets cheaply (then flogging the train/electrics) or by jumping on the occasional cheaply priced selection. Quite often you can buy track with something and sell the something for enough to effectively get the track for free.
There are also some companies/people making some interesting compatible pieces for more advanced layouts (some on eBay, one called trixbrix.eu . None are that cheap.