If the credit card was stolen, it will cost them nothing. If they payed 500 Euro as a fine / bribe / scam, thats 20'000 THB. Nowhere near the 600'000 THB they claim. Sounds more like a scam from their side.
2,1 Million THB for 10 of these towers including installation, foundation, planning, controls and electric work seems weirdly low.... Maybe forgot a digit?