Coloured polythene is more expensive than white. And a heavier duty bag is obviously going to cost you more than a flimsy mass-produced one. What you have to consider is the kind of image you want - and can afford to - project.
All of these carriers are available in three gauges: light, medium and heavy. Medium is recommended for general use.
Bear in mind that the first order will be the most expensive, since the manufacturer will have to make the printing plates. After this the plates will be ready to use whenever you place a new order. There will probably be a minimum order but in the interests of economy, and in the long term this makes sense for both you and the manufacturer.
The design and colours may be more limited but a more elegant finish should probably be a less 'busy' design. You will also be guided by a minimum order - probably around 500. For example prices for a string twisted handle bag might range between 30p and 70p each depending on size and colour(s).
Made in the UK?
It's good to support British industry but the sad fact is that in bag terms it will cost you more to go to a manufacturer here. Carriers made in Europe and even more so in the Far East are much cheaper, particularly when mass-produced.
For example, a top of the range luxury roped carrier might cost up to £2 to produce in the UK whereas a similar item can be made for less than 70p in the Far East.
Taking into account all these decisions, costs and negotiations, you might well come to the conclusion that it isn't worth the hassle. You can buy 500 plastic bags from the cash and carry in one easy stage for very little money.
But it is worth emphasising what a good advert a bag can be - particularly if you have a shop on a high street. An eye catching carrier will remind people who have been to you before that you exist and intrigue other people as to your range of products.