If he’s still doing well, someone may come in for him in January. Even if we did make it to the PL this season, it’s still likely that a bigger club would come in for him. It’s just how it works. It’s why I’m ambivalent about going up - all that happens is that you lose all your best players then get relegated
Swansea City is a business, and money is at the core of it. If a mega offer comes in the next window, why wouldn't the Club sell ? The money could be spent on new face/faces, or the Owners could buy themselves new cars, or a yacht, or two. Their choice. In answer to your question, no Club of Swansea's size would decline a £ 50,000,000.00 offer for Galbraith, or any other of their players.
I suspect that they’d take £15m-£20m if it were offered by someone. Need a bidding war to get anywhere near £50m I suspect
Galbraith has started the season extremely well, and many Club's bigger than Swansea are taking an interest in him, even after just a handful of games. His exposure on the International stage helps elevate him even further, and doubtless the wolves are beginning to circle, and quiet approaches made to his Agent, etc, Swansea got him on the cheap, and those bigger Clubs will be wondering how they managed to achieve that. However, money and personal ambition will dictate what transpires. It always has, and always will. If he maintains good progress, expect some serious January interest. Unearthing such gems is the secret to a successful football Club, so keep digging people. I've got a spare shovel if needed.