Hi,
I consider myself something of an expert on scaples having used them for work every day for the last 19 years.
Firstly, I have to say that I have about a dozen knocking about in various tool boxes - I have lost many over the years, but I still have one of my first two (marked with Yellow reflective tape) so I can say with some certainty that the handles last a lifetime and are worth the investment.
When I'm working, I always have two marked with different coloured tape, one with a sharp blade, one with a dull blade. You'll be suprised how little you need the very sharp poined blade, and a scaple with the first 1mm snapped off can still cut and last you a long time.
When modeling I often have as many as 5 different knives in front of me, as now Swann~Morton make copies of the Xacto range of knives. This is a god-send because as already pointed out, scalpels were designed for cutting open people, not lumps of brass and they do tend to snap! So I always have a couple of knives at hand with sturdier blades for chopping (I like the small square chisel blades for etched brass, my razor blades also see a lot of action).
Anything other than Swann~Morton is false ecconomy! Thier blades are finest Shefield stainless steel, not only can you actually shave with these blades, they hold the edge far longer than any other blade. The plastic handles are a waste of time, never buy them, they will break. The retractable handles are really handy if you want to pocket your knife (Which I frequently do at work) but the locking mechanism will wear out with use, and if you drop them, the arm that holds the blade can bend or break, they rarely last me more than a year. Round handles and long handles are okay, but in my opinion you can't beat a No.3.
As for blades, for some reason they insist on trying to sell you the No.11, in my opinion this blade is too long and thin... using any kind of pressure will make it flex and quite possibly twist which causes loss of accuracy, they are also the easiest to break.
Instead I always buy a box of No.10A -- NOT the No.10 which is the curved blade, but the 10A which is like a No.11 but shorter and fatter. This blade will do anything an 11 will do, but do it better.
I have an account with a Swann-Morton distributor and buy blades in boxes of 100, which costs me about £10+vat last time I bought one for home... the price may have gone up since then because it was about 4 years ago and I still have at least 30 blades left.
I would not recommend that you use pliers to remove the blades... it's doing this sort of thing that will get you into trouble because you are using brute force. Instead, just lift the bottom of the blade with your left hand, and then gripping the top/back of the blade, gently pull with your thumb and forefinger. New handles can be a little stiff, but you should still be able to do it without too much trouble.
Another thing you should do is get a coffee jar, cut a slot in the top like a piggy-bank and use this for disposing of your old blades.