A few points, as this is reviving the Zombie "Krafty is cheap" nonsense. Hopefully this will put a stake in its black heart.
1. The Patriots spend up to the cap like every team does for all intents and purposes. Any money not spent on Moss is inevitably spent on some other player, not banked. So it is not a matter of being "cheap" because the money will be spent regardless. It is a matter of deciding that the value the player will accept is not worth the money that could be better spent elsewhere. That's not being cheap, that's being efficient.
2. Randy Moss was being paid $9 million this year, if I understand correctly. He wanted to extend his contract for another 3 years and likely wanted money somewhere in the same region. He knows that next year there is a lockout and he is 33 years old. Hence he, quite reasonably, wants to make damn sure he's in a position to either put up very good numbers on an offense where he's the main target, or get with a team who will agree to give him an extension of that order of time and money. That team was not going to be the Patriots because they have other contracts they place more value on, and they have a number of good young WR and TE they want to spread the ball around to since the offense was becoming otherwise predictable.
3. It IS a valid argument to say we should have re-signed Seymour, or Vrabel or whomever you are referring to as the ones that got away. I would in that case ask you "just who is it whom we have lost that has gone on to greater things elsewhere anyway?" I can only think of Seymour, but again I understand why we traded one year of his work for a 1st round draft pick.
4. You must necessarily put the salary cap, age, production and likelihood of success in the equation when you want to sign a player. Moss' production is down this year and he's 33. I can accept that the Patriots felt that the deal they could make wasn't the way they wanted to go and so they had to try to come to the best deal they could right now. I can accept that Moss felt he had to make a deal right now while he has leverage so he can ensure that his remaining playing days are paid for to the max. No fault on either side, no problem.
I agree with the others who have commented that you are reacting emotionally to the loss of a player you liked. We liked him too, but we can understand and accept that it happened without ascribing ulterior and nefarious motives to those who made those decisions on both sides.