I was told by the SVR that licencing fees for Thomas are pretty high... Fortunately, whilst my 3yr old is a big train fan, he doesn't exclusively insist on Thomas. In fact, he was quite excited to see King Edward II at Didcot and is urging me to buy a model one. There's going to be a slight issue with the domestic authorities when she realises we have both the DJM version of 6023 and the Hornby blue tts one as well as gwr versions....
When we do visit preserved railways, we tend to use them as our source for big-jigs/Thomas wooden railway items. Whilst you can pick up some of that stuff cheaper, I do prefer for the profit margin to go towards keeping a heritage railway going