Yup we import Coal but Coal is not costly as diesel am i right? :D and also we do also have some coal In india and Regarding Copper & Aluminium wires which you are talking the reason to use Copper not only limited for higher rating of Current the reason is Aluminium wires form Sag in winter seasons which results in Cable to buldge downwards due to its weight and pressure due to which problems arrise for smooth running of pantograph over the wire. And also you might have seen some loads have been connected for Wires near some poles Instead Using Cu wires over aluminium as Cu wire also come accross expansion and contraction same like Rail lines when change in temperatures so to balance their Expansion & Contractions these loads has been hanged and EHV Transmission line have Aluminium i think in india due to Cost...
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Impact but if you go US or saudi arabia or some countries they even use Cu Wires For Transmission lines for Good Efficiency.
Now coming to your Dept Expenses and Wages if you think this way over any Improvements in latest technologuy in Railways or in any field then today whole IR would be on Steam Engines not even on Deisel Also i agree Deisel Engines need less maintenance then steam Engines but Their comes new provisions over new Technology and new things under use so those things need to be considered with cost impact.
Regarding Regular Cut and prune of trees it comes in Maintenance and for proper & Safe Run of trains through the section they will cut the only small amount+ 1.5 to 2 meter extra for considering abnormal natural situations like heavy winds storms where trees which coming near to contact with OHE. you have So many highways pasing through Forests so those cant be the loss for forests?And also Plans to Enhance the lanes for them their wouldnt come Ecology disturbance and Cutting of trees only when Railways do Everybody open eyes this is what going on. Okay Now konkan Passing through Dense forests so do you say its not good to elctrify Konkan route due to all this things wht i found in your comment?

A central theme in most engineering designs is 'trade off'; you can either go extreme on one feature and neglect the rest, or compromise so as to get something of both. similar concept applies here.
When it comes to electrification, there are pros and cons associated with it. it removes the visual aspect of pollution, and is overall quieter but in turn requires multiple substations, 100's of CKM worth of line to bring power to SS, and then another 100+ Km of 25 Kv line to allow electricity to be used on the line. you need additional staff (and money) to maintain those lines, a sophisticated RCC for its monitoring and setup operations department for managing the locos and staff operating them....
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these costs are often offset on lines which see heavy traffic, as there the benefits of e-fication outweigh the cons, especially on cost as the fuel cost of electricity is far lesser than that that of diesel. on plains, especially on frequent start stop trains like EMU's, there is an additional advantage which diesel doesn't offer: regeneration. Regeneration on ghats is too risky owing to its loco only nature, but on plains one can liberally use it, and indeed it saves a lot of costs; CR saved 100's of crores owing to regeneration following shift to AC traction for instance.
This particular line doesn't offer those advantages. Being an isolated ghat line, there will always be a limit to how many trains run on it owing to the very nature of railway operation (only one train can be in a block at a time), most trains here are freight which run continuously, and most importantly, no e-loco in India has creep control, which EMD's have, thereby allowing them tremendous TE. On KR, the line actually operates at rather high loads, and is mostly level gradient, obviating the benefits offered by EMD's monster TE, and electrification would save money by means of regeneration. also, the mountainous nature of the line means that a good chunk of line passes through rock cuttings, areas which are clear of trees, so no pruning etc involved.

OK Abdul bhai mein samaj it was nice explanation regarding pros and cons of Efication on such ghat isolated routes but I was surprised when it got sanctioned for Electrification with single line and also with steep gradients.. and yes I agree EMD is advantageous for creep control. But routes like this are not Electrified one in India some where that's my concern cause if some where such routes got electrified then why not this one? And even Trains both Deisel and Eloco save fuel in coasting period usually can achieve in longer straight downwards journeys where trains run on the own momentum like that their are lot routes designed in IR I think for coasting periods..As u said EMU also good as using regenerative or dynamic braking system which in turn can be feeder to the circuit by this almost 30% of the power feeding to Eloco can be...
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saved.Usually it's more useful in Suburban and Local trains where braking is done almost lot of times in less intervals of time..Yes For Efication their is need of substations in the minimum distance of kms for better feeding to the Electric wires to trains.. so for such SS their needs sure some place and cutting of trees is required. So each one have advantages and disadvantages it's in local ppl and forest dept decision now what to do.. Forest dept can object this RE process..