The problem there is that a deposit that high is considered prohibitive to most sales, if you start charging $150 deposit on a keg, you aren't going to be selling many kegs. Believe me, the idea has been thrown around and shot down every time for that very reason.
One alternative is pubkeg, they are a recyclable, plastic keg that comes form the manufacturer cleaned and pressurized. A reasonable deposit, lower than the average keg deposit in fact, can cover the cost of the keg. They only come in sixtels though, but many bars are moving that way since they can get more beers on tap using the smaller footprint.