Key point is that the player has to relocate entirely the other country first. KP was actually dropped from his domestic side and was playing club cricket before relocating to England, Ronchi was also struggling to get a game for Western Australia, Kepler was a South African who only played for Australia because of the apartheid sanctions against South Africa, Eoin Morgan had very little chance of playing test cricket as an Irish player, Holliake/Strauss/Nasser were developed in the English cricket system, living there since childhood/teenage years
It's not as simple as a country just offering a player a better contract, the player has to want to relocate their entire life as well. Sandhu is an Australian born player with very promising international prospects, and presumably friends and family in Australia. Just don't see him being willing to move.
To be fair I am not sure I agree with the relocation part. What is wrong if say Kohli settled down in Aus, but continued to represent India. For instance to use an example from Chess, Vishy Anand lives in Spain, but plays all his matches under the India flag. Or for that matter in Tennis Vijay Amritraj played Davis Cup for India, despite living abroad for a big period, and similarly his son Prakash Amritraj, despite being born in LA, feels Indian enough to wanna play for India.
I think the key point is the player should be eligible to play for India, and should feel Indian at heart. Where he now resides is irrelevant. Its not a question of just paying off players to play for India, but if we find a player eligible to play for India who is willing to play for India, then go for it by all means. Given the number of NRIs that now live in Eng, Aus or even NZ, I am sure we could find one such pacer atleast.