The first thing you need to know before you purchase kitchen cupboard doors is what material it's made of, what edging will be used on the edges of the door and what finish it will be sprayed, wrapped or manufactured in.
There are five main finishes that cabinet doors are manufactured in. They are PVC vinyl Wrap, veneer, melamine chipboard, Duco spray and solid wood. Solid wood is the most expensive of the five hanging on the type of solid wood you would choose. Pine is obviously much cheaper that any of the other wood types. PVC vinyl wrap is a very common use of bathroom cabinets as well as bedroom and kitchen cabinets. The benefits of PVC vinyl wrap is that the edge of the doors do not pull loose very easily due to the glue that sticks the vinyl to the doors. The core of the door also has to be Supawood so that the edges of the door can be cut out while leaving a smooth finish. Cutting and painting the edges on a chipboard door will not work as the chipboard is far to brittle and will chip away very easily leaving the edged looking very rough.
Veneer doors are more common on kitchen cupboards and can be edged with fleece edging, 1mm-12mm solid impact edging. Impact edging is also used on melamine chipboard doors and is very durable. I normally recommend using impact edging on kitchen cupboards if the client has a flat he or she wanted to renovate and place tenant in. Tenants do not always look after your flat so it would be wise to opt for a more rugged and durable edging on the doors. Lastly we have Duco sprayed doors. This kind of finish is very expensive and not always as unforgiving as PVC vinyl wrap. Although both Duco and vinyl wrap can be finished in a high gloss PVC vinyl does not scratch as easily and scratches can even be polished out to a certain degree if the scratch is not too deep. PVC wrap doors are also almost 50% cheaper than Duco doors. The benefit of Duco sprayed doors is the incredible high gloss finish you get on it. It's almost as if you're looking in a mirror when you look at the door.
In closing. Some doors are cheap and some are expensive but remember if you're going to spend the next 15-20 years in your new kitchen get what you like and not only what fits into the budget. If you have to put Formica work tops in for now but can then afford the doors of your dream do it. You can always remove the Formica tops and replace them with Granite or Solid wood at a later stage.