Possible. I'm more thinking if they are having to move around staff (e.g. stadium staff, potentially paying them to be available to work a reserve day whether it happens or not), broadcast equipment, the teams, officials - not a big problem in England but it could be in Australia or India. Costs of accommodation and transport too.I don’t buy the difficulties reason in this day and age for a format that is as flexible as T20. It’s just the same stubborn rules and traditions cricket sticks to like having a compulsory 30 minute interval to resume matches for rain breaks, going for lunch or tea when the game is almost nearly won with a couple of overs yet to happen and myriad other stories that I forget now.
Could be that washed out matches are insured but if they have a reserve day it could result with a lot of refunds on tickets and running the match at a loss. Although they played matches in front of empty stadiums for a long while during covid.
You would think that the broadcasters would rather have a match a day late than no match. With T20, even if you roll over two matches, there's no reason they couldn't be scheduled to avoid overlap.
Trying to be generous - when it's probably stubborn traditions and greed.