OK, back of the cigarette pack estimate here. Let's create the "Light Indirect Fires Modernization (LIFM) Project" for the Army.
In scope: Acquisition of new howitzers, capable of firing in-service ammunition and capable of being housed in existing infrastructure; related specialized tools and test equipment (STTE); training materials; conversion training.
Out of scope: New ammunition natures; digitization; prime movers, infrastructure; ammunition (existing National Procurement holdings and purchases will sustain this acquisition).
Project office: Assume six personnel for seven years, after which time functions will be handed off to the Life Cycle Materiel Manager. Assume a full cost (including benefits) of $150K per person per year, of $900K/year, or $6.3M for the project life.
Office Space: Set by formula at 20?% of personnel cost; assume $1.26M for the project life.
TD: Assume every member of the PMO travels 4 weeks per year: 3 weeks INCAN, 1 week OUTCAN, and assume a full cost of $2K/week INCAN and $4K/week OUTCAN. That's $60K/year or $420K through the project life.
O&M: Paper, training for PMO staff, snazzy pamphlets that get sent to units years after the fact... call it $40K/year or $280K for the project life.
Total overhead: $8.26M
We are limiting ourselves to a 105 or 155 gun; from a cost perspective, 105 will be less expensive and since we want no infra costs it's also the solution that meets that demand - how many armouries could accommodate 155 guns instead of 105?
So, how many guns? The Res F has 16 Regiments and 3 independent batteries; the Reg F has three gun Regiments (plus whatever it is they do in 4 GS - they will not be included in this), and the RCAS.
If we assume 4 gun batteries, that's (16+3+3) = 22 firing batteries for 88 guns. Plus one for the RCEME school. Plus one reference model. Plus six for the school. Plus four modified to fire blank exclusively for ceremonial functions for 30 Fd (Parenthetic note: Why aren't 30 Fd RCA and the GGFG OPCON to ADM PA, since they're basically PR elements? But I digress...). This takes us to a production run of 100 guns.
How much would training cost? Assume 1000 Res F personnel at an average of $250/day (full cost including PILL and benefits) will each require 5 days of conversion training = $1.25M; add another $1M for ancillary costs associated with conversion training, both Reg and Res, and we're at $2.25M
How much would new guns cost? That's a good question, without much in the way of answers. Best I can find suggests the M777 would run around $8M+ each (Canadian); the last production M198s in current dollars would be around $1.2M each.
If we assume $2M each for new 105 guns (probably L119 under license from a temporary Canadian line set up by GDLS in Windsor), that's $200M.
As we are seeing compatibility with current systems, I'll lowball STTE at $5.49M (and also assume that our "temporary" line, above, will also be contracted for lifecycle maintenance, reducing costs for STTE).
Our total project comes out to: PMO $7.26M; training $2.25M; guns $200M; STTE $5.49M = $215M. Add a 15% contingency, and you're at $247M.
TL;DR: One hundred guns with no infra, no ammo, no digitization, minimal training and tooling would cost, VERY ROUGH estimate, a quarter of a billion dollars.