Rockhopper is right. Root filling alone on the NHS is 53.90 and with a crown it’s £233. Statistically a root filled tooth will last longer if crowned soon afterwards.
In dentistry, like life, you often get what you pay for, both in quality of materials used and time and effort spent by those using them. Crowns particularly are an area where the quality of the item is definitely affected by the materials used.
To give a good example, an old dental lab we used used to have its apprentice technicians making 12 NHS crowns a day. The senior, experienced and more skilled technician did the private ones. He could only make three up to the required standard.