Ok.. Where to start..
First.. No you don't add 10 BPPC for 2000, the cost of 1 is 100... So 2000 for 10 is dumb. Upgrades should either be so big that it saves you a ton of time so you don't mind the cost shift (paying double for a small change you will mind) or it should be (and preferably) the same cost or less of the total for the previous upgrade (so 1000 or less for 10 BPPC). That being said you should have more other upgrades as you advance.
Second.. I like the idea of upgrading your weapon, but with a static value of +10BPPC it quickly becomes useless. It could increase your BPPC x10 and that would be great, or you could give an increase commensurate to the cost each sword is a one of purchase so having increases that are not in line with other costs is fine. 400 for 10 BPPC 2000 for maybe 30-50.. etc.. Cost of these seems to be multiplied by 5 each time?
Third the cost of the sword upgrade should be deducted from your score ... or if you don't want to deduct maybe have the upgrades automatically applied and removed as your score increases/decreases.
Fourth, most clicker games don't need a goal.. Fine, I accept that, but this really feels like it is begging for a goal.. What am I going to battle with all of these battle points? There has to be something more than just buying another sword for hundreds of billions of points?
I do agree that it is a grind even with an autoclicker, and currently that is all that the game is. I am not going to comment on the background or the sprites, those things are nice but they do not make or break a game. Gameplay makes or breaks a game. And this does need work in that area. IMHO work out the gameplay first, worry about making it pretty later. If you happen to fix some of the graphical issues along they way great. If not, I won't personally judge on the graphics until the rest is good. Not going to score it badly, I personally hope you keep working on it and turn it into something really good. Cheers