Between September 2020 and December 2021, Greggs (LSE:GRG) shares soared 184%. Its shares are now (1 August) changing hands for 39% less than they were at the end of 2021. Then and nowThe decline in the Greggs share price appears to result from a slowdown in its sales growth rate and relatively flat earnings. The City viewAnalysts have a consensus 12-month price target of 1,630p, which implies that the group's shares are 18% overvalued. The two extremes mean a £5,000 investment made today, could be worth £3,320 or £5,495 in a year's time.