Like Felix said, most EU countries have burgundy passports. The UK had burgundy passports while still in the EU.

Parts of the UK right wing press and politics stirred up drama about the colour of UK passports during the Brexit debate bemoaning that the dirty, unelected, bureaucratic EU had forced the beautiful, strong, innocent UK to switch from our nationally loved blue passports to their disgusting red ones when we joined the EU.

What really happened is the EU agreed (with UK input) on a standardised layout and design for passports. They did this to make movement around the EU easier and simpler. These agreed standards were guidelines. Each EU member was free to ignore them if they wished. Most use the standard because it makes their life easier. The UK chose to follow the standard, partially because it was one of the designers of the standard.

Because there was a standard colour (burgundy), this meant there was a higher demand for this colour. Higher demand means passport manufacturers prioritise their production for these demands. Prioritised manufacturing meant this colour and style became cheaper. It's not bespoke, it's the standard.

Because the Conservatives and Reform, etc. (the Brexiters) made such a big deal about the colour of UK passports, when Brexit happened they of course had to follow through on changing the passport colours. The result is that UK passports cost more to manufacture now than they did before, and last I checked were manufactured by a company in France! But the Brexiteers believe they've won against the EU by having blue instead of red passports.

It's so embarrassing.