That base kit will cost around 135usd/euros in general. The majority of current sets also go with the big base kit. I have no problem with the current base kit. Remove numpad will only reduce the cost around 10usd/euros based on gmk pricing, remove ISO wont do much either but will lose a lot more interest for people who use ISO (European buyers). If runner are to remove some keys to keep the cost down, remove R1 end and R1 Pgdn and those accent arrows and all Numpad together but the ISO has to be in base kit. Just look at GMK ThinkCaps or GMK Norse, they go with a TKL base and received positive feedbacks about the kitting. The removed keys from base may go to another kits or become a separated kit of its own.
I wouldn't exactly consider ThinkCaps to be a shining beacon of how to Kit GMK though. I had to pass on it because it was just too much to get what I wanted out of it.
Anywho, splitting numpad out of a $130 kit is a good way to turn it into a $150 kit for those that actually want the numpad.
Not saying that's a bad thing, TKL's are certainly popular.
But removing a key here or a key there really won't do much to help the overall cost of the base kit. However, adding a key or two will marginally increase the cost but definitely up your numbers. One good example is including minibars and second B in base for Alice users. That way they're not forced to buy a $50"degenerates" kit for like 3 keys.
What doesn't work so well with GMK is separating out the 40's keys (minivan, ortho, etc) into lots of little kits. Having a comprehensive 40's kit might be expensive but it usually works out pretty well.
I think the kitting looks pretty great as it is. Big base kit is best base kit. I would like to see some love for minivan 1.75u backspace and row 3 1.5u enter though.