The spread compensates for three things: the risk the deal breaks, the time until close, and the financing cost of holding the position. A tight spread means the market is confident; a wide one means real doubt, not free money.
Decompose before trading. Given a downside of $45 on a break and an offer of $60 with the stock at $57, a simple two-outcome model implies a break probability of about 20%. Whether that is cheap depends on the specific regulatory and financing risks, which is the actual research.
Spreads also move with the calendar, tightening as approvals are cleared and widening on adverse news such as a second regulatory request. Cash deals have cleaner spreads than stock deals, where the ratio must also be hedged. See merger-arbitrage.
Related: merger-arbitrage, event-driven, arbitrage, hedge, short-selling, volatility